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UNIVERSITY  OF  ILLINOIS 


Agricultural  Experiment  Station 


BULLETIN  No.  117 


BITTER    ROT  OF   APPLES 

Horticultural  Investigations 


BY  JOSEPH  C.  BLAIR 


URBANA,  ILLINOIS,  AUGUST,  1907 


SUMMARY  OF  BULLETIN  No.  117 

1.  A  series  of  experiments  was  inaugurated  in  1901  and  continued  over 
five  years,  having  in  view  the   determination  of  a  means  of  controlling 
bitter  rot  in  apples.  Page  483. 

2.  Experiments  in  1901.  Page  484. 

3.  Elaborate  precautions  were  taken  to  secure  complete  records  and  ac- 
curate data.  Page  487. 

4.  Experiments  in  1902.  Page  490. 

5.  Spraying  five  times  with   Bordeaux   mixture  before  bitter  rot  ap- 
peared  in  an  orchard  at  Tonti,  in  1902,  resulted  in  a  saving    of  91.26   per 
cent  of  the  crop  liable  to  infection.  Page  491. 

6.  Spraying  from  three  to  five  times  after  the  appearance  of  the  disease 
failed  to  save  any  considerable  part  of  the  crop  in  orchards  at  Tamaroa  and 
Flora  in  1902.  Page  495. 

7.  Experiments  in  1903.  Page  500. 

8.  One  spraying  before  the  appearance  of  bitter  rot  was  not  sufficient 
to     prevent    ravages  of    the     disease    in    an    orchard    at    New  Burnside, 
in  1903.  Page  506. 

9.  Two  sprayings  before  the  appearance  of  the  disease  greatly  reduced 
the  amount  of  bitter  rot,  but  did  not  wholly  control  it  in  an  orchard  at  Car- 
bondale  in  1903.  Page  511. 

10.  The  work  for  1903  was  not  wholly  successful  owing  to  small  crops  and 
light  infections  in  some  of  the  orchards.  Page  512. 

11.  Experiments  in  1904.  Page  512. 

12.  Spraying  the  dormant  wood  with   copper  sulphate   solutions   and 
Oregon  Wash  proved  ineffective  in  preventing  bitter  rot  in  1904.        Page  524. 

13.  Spraying  with  Bordeaux  mixture  after  bitter  rot  infection  had  oc- 
curred was  more  successful  in  preventing  the  disease  during  the  season  of 
1904  than  in  preceding  seasons,  but  was  ineffectual  as  compared  with  sprajT- 
ing  before  the   first  occurrence  of  bitter  rot.  Page  524. 

14.  Experiments  in  1905.  Page  524. 

15.  Scattering  salt  on  the  ground  under  the  trees  had  no  effect  in  con- 
trolling bitter  rot.  Page  527. 

16.  Spraying   with  dust  Bordeaux  mixture  proved  ineffectual  in  check- 
ing bitter  rot.  Page  529. 

17.  Moist  warm  weather  during  July  and  August  was  the  ideal  condi- 
tion for  the  spread  and  development  of  bitter  rot.  Page  541. 

18.  Conclusions.  Page  547' 

19.  Recommendations  for  treatment  of  bitter  rot.  Page  648 


BITTER  ROT  OF  APPLES 
Horticultural  Investigations 

BY  J.  C.  BLAIR,  CHIEF  IN  HORTICULTURE 


During  a  period  of  five  years  the  Department  of  Horticulture  of 
the  University  of  Illinois  has  conducted  investigations  on  the  con- 
trol of  the  disease  known  as  bitter  rot  of  apples,  and  the  Department 
of  Botany  under  the  direction  of  Dr.  T.  J.  Burrill  has  made  an  ex- 
haustive study  of  the  life  history  and  morphology  of  the  fungus 
which  causes  the  disease.  The  results  of  the  work  of  the  two  de- 
partments are  embodied  in  two  bulletins  on  the  bitter  rot  of  apples, 
this  one  detailing  the  results  of  the  horticultural  investigations 
and  having  especial  reference  to  experiments  in  spraying  for  the 
control  of  the  disease,  and  its  companion  bulletin,  No.  118,  compris- 
ing the  results  of  the  botanical  investigations.  The  horticultural 
investigations  were  inaugurated  in  1901  and  were  continued  to  the 
close  of  the  season  of  1905.  Twelve  orchards  were  used  for  the 
work ;  seventeen  series  of  experiments  were  conducted,  experts 
from  the  Experiment  Station  being  placed  in  immediate  charge  to 
insure  the  complete  carrying  out  of  the  experiments  as  planned; 
individual  records  were  made  on  1,269,301  apples,  and  very  full 
and  complete  data  embodying  1728  typewritten  pages  were  com- 
piled from  the  observations  made. 

In  the  material  which  follows,  the  experiments  of  each  year  are 
first  described  separately  and  a  summary  of  the  conclusions  reached 
and  points  unanswered  at  the  close  of  each  year  follows  the  detail- 
ing of  the  results,  after  which  are  given  a  general  summary  of  the 
results  of  the  entire  five  years'  investigations,  a  series  of  conclu- 
sions in  brief  form,  and  a  series  of  recommendations  for  the  control 
of  the  disease. 

483 


484  BULLETIN  No.  117.  [August, 

1901 

In.  April,  1901,  the  Department  of  Horticulture  of  the  Agricul- 
tural Experiment  Station  of  the  University  of  Illinois  began  certain 
experiments,  having  in  view  the  determination  of  the  best  treatment 
for  bitter  rot  of  apples.  In  this  undertaking  it  had  the  cooperation 
of  the  Division  of  Vegetable  Physiology  and  Pathology  of  the 
United  States  Department  of  Agriculture  and  the  Department  of 
Botany  of  the  University  of  Illinois.  The  latter  department  was 
represented  in  this  work  by  Dr.  T.  J.  Burrill  and  the  former  by  Dr. 
Herman  Von  Schrenk,  in  charge  of  the  Mississippi  Valley  Labora- 
tory at  St.  Louis,  operated  by  the  department  first  named  above. 
The  object  of  these  experiments,  as  finally  worked  out  by  all  inter- 
ested, was  to  answer  the  following  questions : 

1.  Can  Bordeaux  mixture  by  proper  spraying  be  made  to  protect 
apples  from  bitter  rot? 

2.  Is  winter  treatment  of  the  dormant  trees  of  any  assistance  in 
the  process  ? 

3.  Is  early  spraying  more  advantageous  than  late  spraying  in 
the  treatment  of  this  disease  ? 

4.  Are  any  other  fungicides  superior  to  Bordeaux  mixture  in  the 
treatment  of  this  special  malady? 

On  account  of  the  great  fluctuations  in  the  amount  of  bitter  rot 
occurring  annually,  the  non-appearance  of  the  disease  during  any 
one  season  in  any  or  all  of  the  experimental  plats  was  anticipated, 
and  the  consequent  uncertain  results  of  the  work,  so  far  as  the  con- 
trol of  the  disease  is  concerned,  would  have  to  be  overcome  by  con- 
tinuing the  operations  through  a  series  of  years.  The  experiments 
were,  therefore,  started  with  the  expectation  of  continuing  them  for 
three  years,  since  any  less  time  would  have  been  insufficient  to  reach 
definite  conclusions.  Because  of  the  failure  of  the  disease  to  appear 
in  some  of  the  orchards  under  experimentation  and  on  account  of 
partial  failures  of  the  apple  crop  in  certain  seasons,  the  work  was 
carried  on  for  two  years  longer,  or,  in  all  five  years. 

The  plan  of  this  experiment  involved  the  laying  off  of  plats,  as 
suggested  below,  in  duplicate  and  in  triplicate,  in  some  commercial 
orchards  in  Illinois,  and  in  giving  these  plats  thorough  spraying  in 
accordance  with  this  plan.  This  plan  was  the  one  followed  in  Mis- 
souri and  in  Virginia  by  the  United  States  Division  of  Vegetable 
Physiology  and  Pathology. 

The  following  is  an  outline  of  the  experiments : 

Plat  I — Winter  spraying  only — Spray  plat  with  Bordeaux  mix- 
ture before  the  buds  swell,  applying  the  spray  until  the  trunk  and 
buds  are  blue. 

Plat  II — Combined  winter  and  spring  spraying — First  treat- 
ment, winter  spraying  before  buds  push;  second  treatment,  when 
cluster  buds  are  open  and  flower  buds  are  exposed;  third  treatment, 


1907.]    BITTER  ROT  OF  APPLES,  HORTICULTURAL  INVESTIGATIONS.      485 

when  the  last  of  the  petals  are  falling;  fourth  treatment,  seven  to 
ten  days  later ;  fifth  treatment,  ten  days  later. 

Plat  III — Early  spraying  without  the  winter  treatment — Same 
as  above  with  first  treatment  left  off;  that  is,  second,  third,  fourth, 
and  fifth  sprayings. 

Plat  IV — Early  spraying  continued  until  summer — second,  third, 
fourth,  and  fifth  sprayings,  with  four  or  five  treatments  more  at  in- 
'tervals  of  two  weeks  until  about  the  middle  of  August. 

Plat  V — Late  spraying — Commenced  when  the  fruit  was  about 
an  inch  in  diameter  and  sprayed  four  or  five  times.  These  sprayings 
were  on  the  same  dates  as  the  last  four  or  five  treatments  of  Plat  IV. 

Late  applications  were  made  with  ammoniacal  copper  carbonate 
solution  on  plats  not  before  treated.  Some  were  made  even  after 
the  disease  had  started,  untreated  trees  outside  of  the  plats  already 
referred  to  being  used  for  the  late  spraying. 

These  experiments  as  outlined  were  undertaken  in  the  orchards 
of  J.  B.  Brokaw  of  Tonti,  N.  B.  Morrison  of  Odin,  and  H.  M.- 
Simpson &  Sons  of  Parkersburg.  The  work  at  Tonti  was  aban- 
doned, so  far  as  the  Experiment  Station  was  concerned,  after  the 
second  application,  owing  to  a  misunderstanding  on  the  part  of  the 
owner  of  the  orchard,  who  sprayed  the  check  plats  as  well  as  those 
which  were  to  receive  the  applications  in  the  schedule.  The  orchards 
at  Parkersburg  and  Odin  were  unattacked  by  bitter  rot,  only  five 
infected  apples  being  found  in  the  entire  crop  at  the  former  place, 
and  none  at  the  latter. 

When  it  became  evident  that  bitter  rot  was  not  likely  to  develop 
to  any  serious  extent  in  the  orchards  at  Parkersburg  and  Odin,  an 
orchard  was  secured  from  Dr.  Daniel  Berry,  near  Carmi,  where 
the  disease  had  made  its  appearance.  Here  it  was  impossible  to  test 
the  value  of  the  winter  treatment  of  the  dormant  wood  or  to  com- 
pare the  value  of  the  early  with  the  late  treatment,  since  only  the 
latter  could  be  applied. 

Five  rows  of  ten  trees  each  were  selected  in  the  worst  infected 
portion  of  the  orchard.  All  were  Ben  Davis  except  one  or  two 
Winesap  and  one  Aiken,  which  were  not  included,  however,  in  the 
picking  of  the  crop.  The  trees  were  about  eighteen  years-  old. 

Applications  were  made  as  follows  :  August  23d  two  rows  were 
given  Bordeaux  mixture  and  two  rows  were  sprayed  with  ammoni- 
acal copper  carbonate  solution,  leaving  one  row  between  as  a  check. 
September  nth  two  of  the  above  rows  were  treated  with  a  second 
application  of  Bordeaux  mixture  and  ammoniacal  copper  carbonate 
solution,  respectively. 

From  four  trees  of  each  sprayed  row  the  infected  apples  were 
removed  (both  from  the  tree  and  from  the  ground)  after  the  first 
application  was  made. 

The  following  table  gives  the  results  of  the  season's  operations. 


486 


BULLETIN  No.  117. 


[August, 


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1907.1      BITTER  ROT  OF  APPLES,  HORTICULTURAL  INVESTIGATIONS.     487 

It  will  be  seen  from  a  perusal  of  the  above  table  that  spraying  in 
most  cases  reduced  the  amount  of  bitter  rot  among  both  windfalls 
and  picked  fruit,  effecting  a  saving  of  from  8  percent  to  14  percent 
of  the  entire  crop,  or  from  40  percent  to  61  percent  of  the  fruit 
liable  to  infection  (Plats  VIII  and  VI,  respectively).  In  Plats  II, 
III,  and  IX,  however,  the  percentages  of  rot  ran  very  high  in  spite 
of  the  spraying,  indicating  either  that  these  plats  were  more  severely 
infected  than  the  others  or  that  the  spray  was  ineffective  in  prevent- 
ing the  ravages  of  the  disease.  It  is  probable  that  both  causes  af- 
fected the  result  somewhat  for  even  in  Plat  VI,  where  the  control 
was  most  complete,  the  protection  was  far  from  perfect.  The  results 
clearly  indicate,  therefore,  that  spraying  but  once  or  twice  with 
Bordeaux  mixture  or  copper  carbonate  solution  is  not  a  perfectly 
effectual  way  of  controlling  bitter  rot.  The  removal  of  affected 
fruits,  too,  apparently  failed  to  prevent  the  spread  of  the  disease. 

CONCLUSIONS  FOR  1901 

While  the  work  during  1901  yielded  no  data  of  sufficient  con- 
clusiveness  to  warrant  definite  recommendations  for  the  treatment 
of  bitter  rot,  it  as  least  served  the  useful  purpose  of  pointing  out 
lines  along  which  the  work  should  be  conducted  in  succeeding  sea- 
sons. Particularly  was  it  valuable  in  emphasizing  the  necessity  of 
having  all  conditions  of  the  plats  under  as  perfect  control  as  the 
nature  of  the  experiment  would  permit.  In  the  work  of  1902  and 
in  all  subsequent  work  every  care  was  taken  to  make  the  experimen- 
tal conditions  as  perfect  as  possible.  The  following  important  fac- 
tors were  especially  considered  in  conducting  the  investigations : 

i.  The  Infection  Factor: — The  success  of  experimental  work  in 
spraying  for  any  disease  must  be  very  largely  dependent  on  the 
uniformity  and  amount  of  infection  of  the  plats  under  consideration. 
If  the  infection  is  not  uniform  throughout,  inaccuracy  in  results  is 
bound  to  occur  unless  very  complete  precautions  are  taken  to  over- 
come the  influence  of  variable  infection.  If  the  amount  of  infection 
is  very  slight  in  all  the  plats,  no  wide  differences  in  results  can  occur, 
and  small  differences  leave  doubt  as  to  whether  the  results  are  to  be 
ascribed  to  fluctuations  in  infection  or  to  differences  in  the  treat- 
ments of  the  various  plats  under  investigation. 

In  case  of  bitter  rot  of  apples  the  infection  factor  was  found  to 
be  exceedingly  variable  and  very  difficult  of  control,  and  the  follow- 
ing precautions  were  taken  to  eliminate  its  unevenness  and  uncer- 
tainty. 

(a)  In  all  experiments  orchards  were  selected  which  in  previous 
years  had  been  severely  and  uniformly  attacked  by  bitter  rot,  and  in 
which  it  was  confidently  expected  that,  in  a  season  at  all  favorable 
to  the  development  of  the  disease,  bitter  rot  would  be  present  in 
sufficient  quantities  for  experimental  purposes. 


488  BULLETIN  No.  117.  [August, 

(b)  The  experience  of  1901  having  shown  that  the  precaution 
of  selecting  orchards  known  to  have  been  infected  in  previous  years 
was  insufficient  to  insure  good  experimental  conditions  for  investi- 
gations on  spraying  for  bitter  rot  in  any  particular  season,  plans 
were  made  to  continue  experimental  work  over  a  series  of  years 
in  certain  orchards,  and  thus  insure  satisfactory  conditions  at  some 
time  or  other  during  the  progress  of  the  experiments,  and  eliminate 
by  large  totals  the  effects  of  uneven  or  uncertain  infection. 

(c)  A  large  number  of  orchards  were  used  in  the  experiments 
in  order  to  lessen  the  factor  of  variability  in  infection.    In  all,  twelve 
orchards  were  employed  and  some  seventeen  series  of  experiments 
were  conducted  in  the  course  of  the  five  years  of  bitter  rot  investi- 
gation. 

(d)  As  a  further  precaution  the  plats  of  trees  were  made  un- 
usually large,  for  investigations  of  this  kind,  numbering  for  the 
most  part  from  fifteen  to  thirty  or  more  trees  to  the  plat,  with  con- 
trol plats  of  at  least  ten  trees  each.     Where  more  than  three  plats 
were  concerned  in  an  experiment,  as  was  the  case  in  most  of  the 
orchards  selected  for  work  during  1903,  1904,  and  1905,  two  or 
more  check  or  control  plats  were  reserved  in  each  series  in  order 
that  the  amount  of  infection  in  each  part  of  the  orchard  might  be 
more  accurately  measured  and  adjoining  plats  compared  therewith. 

2.  The  Crop  Factor : — The  amount  of  the  crop,  in  a  number  of 
instances,  proved  to  be  an  exceedingly  important  consideration  in 
the  experimentarwork  with  bitter  rot.  The  years  1901,  1903,  1904, 
and  1905  were  all  more  or  less  unfavorable  for  the  apple  crop  in 
Illinois,  and  on  this  account  certain  of  the  experimental  orchards 
yielded  disappointing  returns.  Where  the  crop  was  light  and  scat- 
tering the  disease  spread  much  less  rapidly  than  where  the  crop  was 
large  and  the  apples  hung  closely  together.  Thus  the  infection  in 
these  orchards  was  less  uniform  than  in  orchards  producing  good 
crops.  Moreover,  in  certain  orchards  the  crop  was  so  light  as  to 
make  the  investigations  of  comparatively  little  value,  one  or  two 
series  of  experiments  being  abandoned  on  account  of  the  failure  of 
the  trees  to  set  a  crop  of  apples. 

The  measures  taken  to  guard  against  failure  of  the  experiment 
through  failure  of  the  crop  were  practically  the  same  as  those 
adopted  to  guard  against  failure  from  uneven  and  uncertain  infec- 
tion, i.  e.,  continuing  the  experiment  over  a  considerable  number  of 
years,  conducting  experiments  in  several  orchards  each  year,  and 
using  large  numbers  of  trees  in  each  plat.  In  addition  to  these  pre- 
cautions, where  the  plan  of  the  experiment  would  permit  it,  or- 
chards were  chosen  for  experimental  work  after  the  fruit  had  set, 
as  in  the  Allen  orchards  near  Carbondale  in  1903,  thus  practically 
insuring  a  crop. 


V 

1907.]     BITTER  ROT  OF  APPLES,  HORTICULTURAL,  INVESTIGATIONS.     489 

3.  The  Weather  Factor : — The  weather  factor  is  so  closely  as- 
sociated with  the  infection  factor  as  to  need  only  passing  mention 
in  that  connection.     But  it  is  also  important  in  its  influence  on  the 
treatments  given  the  various    plats,  since    heavy     rains    wash  off 
some  of  the  spray  materials    and  thus  unavoidably  interfere  to  a 
greater  or  lesser  extent  with  the  plan  of  the  experimenter.     Again 
the  only  recourse  of  the  investigator  is  to  extend  his  observations 
over  a  series  of  years  and  average  his  results  or  wait  for  favorable 
conditions. 

4.  The  Variety  Factor: — Certain  varieties  have  been  found  to 
be  more  susceptible  to  bitter  rot  than  others,  though  it  is  probable 
that  no  variety  is  entirely  immune  from  the  disease.     For  the  sake 
of  uniformity,  therefore,  the  most  of  the  work  was  confined  to  the 
Ben  Davis,  a  variety  which  is  fairly  subject  to  the  disease  and  is 
more  extensively  grown  in  the  bitter  rot  regions  of  Illinois  than  any 
other.    A  very  complete  series  of  experiments  was  carried  on,  how- 
ever, in  an  orchard  at  Flora,  with  the  Willow  Twig  variety,  an  apple 
notoriously  susceptible  to  the  bitter  rot  fungus,  and  a  few  isolated 
experiments  were  conducted  on  Jonathan,  Winesap,  and  Huntsman 
varieties  in  other  orchards  at  various  times.    For  the  most  part  the 
experiments  were  made  in  blocks  of  trees  composed  almost  wholly 
of  one  variety,  and  in  cases  where  the  plats  contained  more  than  one 
variety  the  results  for  each  are  recorded  separately. 

5.  Factor  of  Preparation  and  Application  of  Spraying  Materials : 
In  the  work  of  1902  and  in  all  subsequent  seasons  every  care  was 
taken  to  follow  the  spraying  schedule  exactly  throughout  the  season. 
The  experimental  orchards  were  placed  immediately  in  charge  of 
employees  of  the  Horticultural  Department,  the  employee  in  charge 
remaining  at  the  orchard  throughout  the  entire  season  to  conduct 
the  experiment  and  make  the  records.     Thus  the  preparation  and 
application  of  the  spray  mixtures  was  attended  to  directly  by  expert 
men.    Good  fresh  chemicals  were  used  each  season  and  the  mixtures 
applied  were  prepared  in  accordance  with  the  most  approved  spray- 
ing practice.    In  this  way  the  chances  for  error  in  this  direction  were 
reduced  to  a  minimum. 

But  in  spite  of  all  precautions  disappointments  were  more  fre- 
quent than  were  complete  successes  in  the  results  which  were  ob- 
tained during  the  four  seasons  of  1901,  1902,  1903,  and  1904. 
Small  crops  in  some  of  the  orchards,  failure  of  bitter  rot  to  appear 
in  some  orchards,  and,  in  spite  of  the  large  plats  and  the  careful 
choice  of  orchards,  the  very  uneven  distribution  of  the  infection  in 
others,  were  responsible  for  the  inconclusive  results  which  were 
obtained  from  several  of  the  experiments.  In  a  number  of  orchards, 
however,  conditions  proved  very  favorable  for  the  performance  of 
the  experiments,  and  uniform  and  satisfactory  data  were  obtained 


490  BULLETIN  No.  117.  [August, 

therefrom  which  appear  sufficiently  significant  to  be  used  as  a  basis 
for  certain  definite  recommendations  for  the  prevention  and  control 
of  bitter  rot  of  apples. 

1902 

The  work  for  1902,  which  from  this  time  to  the  conclusion  of 
the  experiments  was  carried  on  independent  of  the  Federal  authori- 
ties, was  carefully  planned  with  a  view  of  determining  the  following 
points : 

1.  The  value  of  early  sprayings  repeated  at  intervals  of  ten  days 
up  to  the  time  of  the  appearance  of  the  disease. 

2.  The  value  of  spraying  shortly  before  the  appearance  of  the 
disease. 

3.  The  value  of  three  applications  of  spraying  material  at  in- 
tervals of  ten  days,  beginning  after  the  appearance  of  the  disease. 

4.  The  value  of  five  applications  of  spraying  material,  at  inter- 
vals of  ten  days,  beginning  after  the  appearance  of  the  disease. 

5.  The  value  of  making  applications  after  every  rain,  beginning 
after  the  appearance  of  the  disease. 

Three  orchards  were  selected  in  which  it  seemed  probable  from 
past  records  that  the  rot  would  surely  develop.  These  orchards 
were  located  near  Tonti,  Tamaroa,  and  Flora.  In  order  that  the 
operations  might  be  carried"  forward  on  a  sufficiently  large  scale 
to  render  the  results  of  practical  value  and  leave  no  uncertainty 
regarding  the  conclusions,  it  was  decided  to  undertake  the  investiga- 
tion of  only  a  part  of  the  above  enumerated  points  in  each  orchard. 
Accordingly  the  operations  at  Tonti  were  carried  on  with  a  view  of 
determining  the  first  two  points;  the  operations  at  Tamaroa,  the 
third  and  fourth  points ;  and  those  at  Flora,  the  fourth  and  fifth 
points.  In  all  of  the  orchards  check  plats  were  left  unsprayed  for 
purposes  of  comparison* 

The  material  used  in  all  of  the  spraying  was  Bordeaux  mixture 
of  the  usual  strength — four  pounds  lime,  four  pounds  copper  sul- 
phate, and  fifty  gallons  water. 

ORCHARD  OF  J.  B.  BROKAW,  TONTI,  MARION  COUNTY,  1902 

Three  plats  consisting  of  fifteen  or  more  trees  each  were  laid 
out  in  this  orchard,  all  the  trees  in  each  plat  being  Ben  Davis  with 
the  exception  of  two  Huntsman  located  at  one  end  of  the  block,  in 
all  six  trees  of  the  Huntsman  equally  divided  among  the  three  plats. 

Plat  I  was  sprayed  with  Bordeaux  mixture  May  I5th,  28th, 
June  7th,  and  I7th.  The  spraying  designed  for  June  27th  was 
abandoned  on  account  of  the  soft  ground  resulting  from  almost  con- 
tinuous rains,  and  July  2d,  when  the  Ben  Davis  trees  were  sprayed, 


1907.]     BITTER  ROT  OF  APPLES,  HORTICULTURAL  INVESTIGATIONS.     491 

it  was  impossible  to  reach  the  Huntsman  which  were  located  on 
somewhat  lower  ground  than  the  rest  of  the  plat.  Thus  the  Hunts- 
man were  not  sprayed  until  July  gth. 

Plat  II  was  sprayed  with  Bordeaux  mixture  May  I5th,  July 
2d,  9th,  and  I2th,  excepting  the  Huntsman  which  received  their 
first  application  July  9th  and  the  second  one  July  I3th. 

Plat  III  was  not  sprayed. 

On  account  of  the  somewhat  different  treatment  of  the  Ben 
Davis  and  the  Huntsman  trees  in  this  experiment,  and  on  account 
of  the  greater  susceptibility  of  the  latter  to  bitter  rot  fungus,  the 
results  of  the  work  in  the  Tonti  orchard  will  be  given  in  separate 
tables.  Records  of  fallen  apples  were  made  July  9th,  28th,  3  ist, 
August  8th,  1 3th,  2oth,  28th,  September  9th,  2Oth,  3Oth,  and  Octo- 
ber ist.  All  infected  apples  were  counted  as  were  also  those  free 
from  rot  at  each  picking.  September  3Oth  and  October  ist  the 
apples  were  picked  from  the  trees,  examined  and  counted,  and  rec- 
ord made  of  the  number  of  specimens  showing  bitter  rot  and  of  the 
total  number  of  specimens  in  the  crop.  The  results  are  shown  in 
Table  2. 

While  the  results  of  the  experiment  in  the  Brokaw  orchard  as 
shown  in  the  above  tabulation  are  not  conclusive,  there  is  consider- 
able evidence  to  show  that  spraying  may  be  effective  in  checking 
bitter  rot.  44.95  percent  of  all  the  fruit  on  the  Ben  Davis  trees 
which  were  not  sprayed  was  attacked  by  bitter  rot,  whereas  only 
3.93  percent  was  affected  in  the  early  sprayed  plat,  a  saving  of  91.26 
percent  of  the  fruit  liable  to  attack  by  bitter  rot,  where  the  trees 
were  sprayed  five  times  before  any  rot  appeared.  Spraying  once 
shortly  before  the  rot  appeared  and  twice  afterwards  also  checked 
the  disease,  effecting  a  saving  over  the  check  plat  of  63.00  percent 
of  the  fruit  liable  to  bitter  rot.  In  this  respect,  however,  the  earlier 
sprayings  proved  considerably  the  more  effective. 

In  the  Huntsman  the  percentage  of  rot  in  all  plats  was  very 
much  higher  than  in  the  Ben  Davis.  It  will  be  remembered,  how- 
ever, that  in  the  case  of  the  early  sprayed  plat  two  very  important 
applications  of  Bordeaux  had  to  be  omitted  on  account  of  difficulty 
in  getting  to  the  trees,  those  of  June  27th  and  July  2d,  leaving  a 
period  of  twenty-two  days  between  sprayings  in  the  case  of  Plat  I 
of  the  Huntsman,  so  that  when  the  spray  was  finally  applied  the  bit- 
ter rot  infection  was  already  quite  general.  Even  then  there  was 
effected  a  saving  of  38.66  percent  over  the  check  plat  and  of  34.45 
percent  over  the  plat  sprayed  after  the  rot  appeared.  The  discour- 
aging part  about  the  Huntsman  experiment  is  the  very  small  number 
of  apples  which  remained  on  the  tree  until  picking  time.  Such  -apples 
as  did  remain,  however,  were  all  found  on  the  sprayed  plats. 


492 


BULLETIN  No.  117. 


[August, 


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1907.]     BITTER  ROT  OF  APPLES,  HORTICULTURAL  INVESTIGATIONS.      493 


The  following  table  gives  the  relative  percentages  of  saving  ef- 
fected by  the  different  treatments  applied : 

TABLE  3, — SAVINGS  EFFECTED  BY  SPRAYING  IN  THE  TONTI  ORCHARD  IN  1902 


No.  of 

plat. 

Treatment. 

Saving- 
over 
plat  II. 

Saving 
over 
check 
III. 

I 

Ben  Davis 

Sprayed  five  times  before  any  rot  appeared, 
once  afterwards  

Percent- 
age 

76  37 

Percent- 
age 

91  26 

II 

Sprayed  once  shortly  before  any  rot  appeared 
and  twice  soon  after  it  appeared  

63.00 

I 

Huntsman 

Sprayed  four  times  before  any  rot  appeared 
and  twice  afterwards  

34  45 

38  66 

II 

Sprayed  twice  after  the  rot  appeared  

6  42 

Conclusions : — In  so  far  as  this  experiment  was  expected  to  an- 
swer the  question  of  the  relative  efficiency  of  early  and  late  applica- 
tions of  the  spray,  it  is  clearly  in  favor  of  the  early  spraying. 

ORCHARD  OF  F.  L.  WIUJAMS  &  SON,  TAMAROA,  PERRY  COUNTY, 

1902 

The  Ben  Davis  variety  of  apples  was  the  only  one  experimented 
with  in  this  block.  One  application  of  Bordeaux-Paris  green  mix- 
ture was  made  by  the  owner  of  the  orchard  May  ist.  This  appli- 
cation was  for  the  purpose  of  controlling  apple  scab  and  codling 
moth.  Three  plats  of  fifteen  trees  each  were  reserved  for  the  ex- 
periment and  were  treated  as  follows,  the  object  being  to  test  the 
value  of  different  numbers  of  late  applications  for  the  suppression  of 
bitter  rot : 

Plat  I  was  sprayed  with  Bordeaux  mixture  after  the  disease  had 
become  thoroughly  established,  July  i6th,  26th,  August  6th,  i6th, 
and  27th,  in  all,  five  times. 

Plat  II  \vas  sprayed  with  Bordeaux  mixture  after  the  disease 
had  become  thoroughly  established,  July  i6th,  26th,  and  August 
6th,  in  all,  three  times. 

Plat  III  was  not  sprayed. 

Bitter  rot  was  first  discovered  in  the  plats  July  5th.  Records 
on  the  fallen  apples  were  made  July  2Qth,  August  8th,  i6th,  22d, 
27th,  September  3d,  roth,  iQth,  and  October  8th.  Records  of  in- 
fected and  non-infected  fruit  were  made  similar  to  those  at  the 
Tonti  orchard.  The  apples  were  picked  from  the  trees  October  6th, 
7th,  and  8th,  and  the  records  when  completed  furnished  data  for 
Table  4. 


494 


BULLETIN  No.  117. 


[August, 


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1907.]    BITTER  ROT  OF  APPLES,  HORTICULTURAL  INVESTIGATIONS.       495 


It  will  be  seen  from  Table  4  that  bitter  rot  developed  to  a 
considerably  greater  extent  in  the  Tamaroa  orchard  than  in  the 
Tonti  orchard,  the  check  plat  in  the  former  showing  an  infection 
of  68.54  percent  and  the  latter  an  infection  of  44.95  percent  for  the 
Ben  Davis.  So  far  as  the  effect  of  the  spray  in  controlling  the  dis- 
ease is  concerned  the  results  only  indicate  that  it  was  markedly  in- 
effective. Even  five  applications  failed  to  save  any  large  amount  of 
the  crop,  48.26  percent  of  the  entire  crop  being  affected  with  the 
disease,  as  compared  with  68.54  percent  for  the  check  plat.  The 
results  for  the  picked  fruit  alone  are  somewhat  more  favorable  to 
both  the  sprayed  plats,  only  20.37  percent  of  the  picked  fruit  on 
Plat  I  and  28.09  percent  on  Plat  II  being  infected,  as  compared  with 
49.20  percent  on  the  check  plat. 

The  following  table  shows  the  saving  in  percentages  effected  by 
each  treatment : 

TABLE  5. — SAVING  IN   PERCENTAGES   EFFECTED   BY  SPRAYING  IN  THE 
TAMAROA  ORCHARD  IN  1902 


NO;  of 

plat. 

Treatment. 

Saving 
over 
plat  II. 

Saving 
over 
check 
III. 

I 

Sprayed  five  times  after  disease  was  fully  es- 
tablished   

Percent- 
age 

19.51 

Percent- 
age 

29  59 

II 

Sprayed  three  times  after  disease  was  fully 
established  

12  52 

Conclusions: — Late  spraying  had  some  effect  in  decreasing  the 
amount  of  injury  done  by  bitter  rot.  Five  late  sprayings  effected  a 
saving  over  three  sprayings,  of  19.51  percent,  and  over  the  check 
plat,  of  29.59  percent  of  possible  infection  of  bitter  rot,  but  as  com- 
pared with  the  early  spraying  in  the  Tonti  orchard,  it  was  much 
less  effective  in  controlling  the  disease. 

ORCHARD  OF  DALE  MANN,  FLORA,  CLAY  COUNTY,  1902 

In  this  orchard  but  one  variety  was  under  treatment,  the  Willow 
Twig.  The  block,  excepting  the  check  plat,  was  sprayed  just  after 
the  petals  fell  and  again  two  weeks  later,  by  the  owner  of  the  or' 
chard.  This  was  for  scab  and  codling  moth  and  not  a  part  of  the 
regular  experimental  work.  As  in  the  Tonti  and  Tamaroa  orchards 
three  plats  of  fifteen  trees  each  were  laid  out,  the  object  being  a 
comparison  of  the  value  of  spraying  at  regular  intervals  of  ten  days 


496  BULLETIN  No.  117.  [August, 

after  the  appearance  of  the  rot  with  spraying  after  every  rain  after 
the  appearance  of  the  rot.  It  happened,  however,  that  rain  fell  just 
previous  to  the  regular  time  for  spraying  throughout  the  entire  sea- 
son and  hence  the  two  sprayed  plats  received  the  same  treatments. 
The  plats  were  sprayed  as  follows  : 

Plat  I — This  plat  was  to  be  treated  after  the  bitter  rot  became 
established  and  all  subsequent  applications  were  to  be  governed  by 
weather  conditions.  Following  out  this  program  applications  were 
made  July  I4th,  25th,  August  5th,  I5th,  and  25th.  On  the  date  of 
the  first  application  infection  of  bitter  rot  was  found  to  be  general 
throughout  the  orchard.  Rains  occurred  just  before  each  of  the 
applications  above  referred  to. 

Plat  II — Sprayed  with  Bordeaux  mixture  every  ten  days  re- 
gardless of  rain,  July  I4th,  24th,  August  5th,  I5th,  and  25th. 

Plat  III — Check  plat,  not  sprayed. 

Records  on  the  fallen  apples  were  made  July  25th,  3Oth,  August 
5th,  1 5th,  2  ist,  25th,  September  ist,  8th,  i/th,  24th,  and  Octo- 
ber 1 5th. 

The  fruit  was  picked  from  the  trees  October  i4th  and  I5th,  the 
apples  were  counted,  and  the  records  completed. 

The  results  of  the  experiments  in  this  orchard  are  tabulated  in 
Table  6. 

The  average  percentage  of  bitter  rot  for  the  two  sprayed  plats 
is  59.89  percent.  This  shows  that  an  average  of  23.43  percent  of 
the  entire  crop  was  saved  by  spraying  five  times  after  the  appearance 
of  the  disease;  that  is,  the  percentage  of  the  crop  saved  was  about 
the  same  as  in  the  case  of  the  Ben  Davis  receiving  similar  treatment 
at  Tamaroa.  The  percentage  of  rot  in  the  check  plat,  83.32,  shows 
that  the  Willow  Twig  at  Flora  was  attacked  worse  than  the  Ben 
Davis  at  Tamaroa  or  Tonti,  and  nearly  as  bad  as  the  Huntsman  at 
the  latter  place.  In  this  table  the  most  interesting  results  from  the 
orchardists'  view  point  appear  in  the  column  of  picked  fruits.  The 
saving  effected  by  the  spraying  in  the  case  of  the  two  sprayed  plats 
was,  taking  the  average  for  Plats  I  and  II,  36.85  percent  of  the 
fruit  picked,  and  at  the  same  time,  the  total  proportion  of  fruit 
remaining  upon  the  sprayed  trees  was  almost  four  times  greater 
than  that  remaining  upon  the  unsprayed  trees. 


1907.]    BITTER  ROT  OP  APPLES,  HORTICULTURAL  INVESTIGATIONS.       497 


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498  BULLETIN  No.  117.  [August, 

The  saving  in  percentages  of  the  crop  liable  to  bitter  rot  effected 
by  the  spraying  is  as  follows : 

TABLE  7.— SAVING  EFFECTED  BY  FIVE  SPRAYINGS  AFTER  THE  APPEAR- 
ANCE OF  THE  DISEASE 


No.  of 
plat. 

Treatment. 

Saving 
over 
plat  II. 

Saving 
over 
check 
III. 

Average,  sprayed  five  times  after  the  disease 

28.12 

Of  the  picked  crop  an  apparent  saving  in  apples  liable  to  infec- 
tion of  70.46  percent  was  effected. 

Conclusions: — Owing  to  the  peculiar  weather  conditions  which 
prevailed  during  the  season  of  1902  this  experiment  failed  to  an- 
swer the  question  as  to  whether  spraying  at  regular  intervals  after 
the  appearance  of  the  rot,  regardless  of  weather  conditions,  was  more 
or  less  efficient  than  spraying  after  every  rain.  It  did,  however, 
show  that  spraying  after  the  appearance  of  the  rot  would  check  the 
disease,  though  in  this  instance  not  completely  enough  to  be  recom- 
mended commercially. 

The  results  of  the  experimental  work  in  1902  are  briefly  summed 
up  in  Table  8,  page  499. 

CONCLUSIONS  FOR  1902 

1.  In  every  instance  spraying  reduced  the  damage  done  by  bit- 
ter rot. 

2.  The  saving  effected  by  spraying  varied  from  91.26  percent  of 
the  total  infection  possible,  as  shown  by  the  check  plats,  to  6.42 
percent. 

3.  Spraying  five  times  before  the  rot  appeared  and  once  after- 
wards proved  by  far  the  most  efficacious  preventive  of  the  disease. 

4.  Spraying  after  the  disease  appeared  prevented  fresh  infections 
but  did  not  save  the  fruits  already  attacked. 

5.  Huntsman  and  Willow  Twig- apples  were  more  susceptible 
to  bitter  rot  than  Ben  Davis. 

6.  The  securing  of  a  thorough  coating  of  Bordeaux  mixture  on 
the  apples  before  the  first  appearance  of  the  disease  was  more  im- 
portant than  spraying  at  stated  intervals  with  reference  to  time 
and  rains. 

7.  Since  the  bitter  rot  appeared  earlier  than  usual  in  1902,  the 
first  and  most  general  infection  occurring  between  June  26th  and 
July  2d,  it  would  seem  that  the  early  spraying  should  be  done  be- 
tween June  ist  and  25th,  and,  if  necessary,  the  coating  of  Bordeaux 
mixture  be  maintained  by  later  applications. 


1907.}    BITTER  ROT  OP  APPLES,  HORTICULTURAL  INVESTIGATIONS.      499 


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500  |         BULLETIN  No.  117.  [August, 

1903 

The  work  for  1903  was  planned  along  lines  similar  to  that  for 
the  preceding  year;  plats  being  laid  out  as  before  at  Olney,  Flora, 
and  Tamaroa.  This  season,  however,  was  a  most  unfortunate  one, 
very  few  apples  setting  in  any  of  the  orchards  and  consequently 
work  was  abandoned  at  Flora,  while  in  the  Olney  and  Tamaroa  or- 
chards work  was  carried  through,  hoping  that  the  scattered  fruit 
might  develop  a  sufficient  amount  of  the  disease  to  warrant  the 
drawing  of  some  conclusions.  When  it  was  found  that  these  re- 
sults were  not  likely  to  be  of  a  very  definite  character,  orchards  were 
selected  at  Carbondale  and  New  Burnside,  where  it  was  known  that 
there  was  considerable  bitter  rot  in  preceding  years  and  where  the 
rot  for  this  particular  season  was  very  promising.  It  was  designed 
to  answer  the  following  problems  by  means  of  these  experiments : 

1.  The  value  of  spraying  dormant  wood  in  the  fall  with  a  cop- 
per sulphate  solution  containing  one  pound  of  the  sulphate  to  fifteen 
gallons  of  water. 

2.  The  value  of  spraying  dormant  wood  in  the  spring  with  a 
copper  sulphate  solution  containing  one  pound  of  the  sulphate  to 
fifteen  gallons  of  water. 

3.  The  value  of  spraying  three  times  in  July  with  Bordeaux 
mixture. 

4.  The  value  of  spraying  at  intervals  of  ten  days  after  the  first 
three  sprayings  until  after  July  ist  with  Bordeaux  mixture. 

5.  The  value  of  spraying  four  times  in  June  at  weekly  intervals 
with  Bordeaux  mixture. 

6.  The  value  of  spraying  so  as  to  coat  the  fruit  thoroughly  with 
Bordeaux  mixture  when  bitter  rot  first  appears. 

J.  The  value  of  spraying  so  as  to  coat  the  fruit  thoroughly  with 
Bordeaux  mixture  after  bitter  rot  has  become  thoroughly  estab- 
lished. 

The  Bordeaux  mixture  used  in  spraying  for  bitter  rot  in  these 
experiments  consisted  of  four  pounds  of  copper .  sulphate  and  four 
pounds  of  lime  to  fifty  gallons  of  water.  Applications  of  spray 
made  early  in  the  season  for  scab,  canker  worm,  and  codling  moth 
consisted  of  Bordeaux  mixture  prepared  as  for  bitter  rot  to  which 
was  added  four  ounces  of  Paris  green.  Plats  which  were  reserved 
as  checks  received  only  the  early  sprayings  for  scab,  canker  worm, 
and  codling  moth. 

ORCHARD  OF  J.  L.  ZOOK,  OLNEY,  RICHLAND  COUNTY,  1903 

The  variety  selected  in  this  orchard  was  Ben  Davis.  The  trees 
were  located  on  a  comparatively  level  tract  in  the  heart  of  a  large 
commercial  orchard.  Nine  plats  were  laid  out,  all  of  which  con- 


1907.]     BITTER  ROT  OF  APPLES,  HORTICULTURAL  INVESTIGATIONS.      501 

tained  fifteen  bearing  trees  with  the  exception  of  check  plat  No.  3, 
which  contained  only  ten  trees.  All  plats  received  two  applications 
of  spray  for  scab  and  codling  moth,  the  first  just  after  the  petals 
had  fallen,  April  3Oth,  and  the  second,  one  week  later,  May  7th 
and  8th.  After  this  the  plats  were  treated  as  follows  : 

Plat  I — Sprayed  with  copper  sulphate  solution,  one  pound  to 
fifty  gallons  of  water,  November  24,  1902. 

Plat  II — Sprayed  with  copper  sulphate  solution,  one  pound  to 
fifty  gallons  of  water,  March  28,  1903. 

Plat  III — Check  plat,  not  sprayed  for  bitter  rot. 

Plat  IV — Sprayed  with  Bordeaux  mixture  July  2d,  nth, 
and  2 1  st. 

Plat  V — Sprayed  with  Bordeaux  mixture  May  i8th,  28th,  June 
6th,  1 8th,  27th,  and  July  8th. 

Plat  VI — Sprayed  with  Bordeaux  mixture  June  5th,  nth,  i8th, 
and  25th. 

Plat  VII — Check  plat,  not  sprayed. 

Plat  VIII — This  plat  was  to  have  been  sprayed  as  soon  as  rot 
appeared  but,  as  the  disease  was  almost  wholly  wanting,  this  treat- 
ment was  not  given. 

Plat  IX — This  plat  was  to  have  been  sprayed  when  the  disease 
became  permanently  established  but  this  treatment  was  withheld  as 
in  the  case  of  the  treatment  for  Plat  VIII. 

The  disease  was  first  noticed  August  7th.  Records  of  fallen 
apples  were  made  July  27th,  August  loth,  2Oth,  25th,  September 
3d,  1 5th,  and  October  I4th.  The  crop  was  picked  from  the  trees 
October  I4th.  Table  9  shows  the  amount  of  bitter  rot  which  de- 
veloped under  each  treatment : 

Nt>  conclusions  whatever  are  to  be  drawn  from  the  work  in  the 
Olney  orchard  for  1903.  The  very  slight  fluctuations  between  plats 
may  easily  be  the  result  of  slight  circumstances  of  variation  impos- 
sible of  control  in  an  orchard  experiment,  as  for  example  a  few  more 
centers  of  infection  in  one  plat  than  another,  differences  in  crop,  and 
other  conditions  more  or  less  difficult  of  discernment. 

ORCHARD  OF  F.  L.  WILLIAMS  &  SON,  TAMAROA,  PERRY  COUNTY, 

1903 

The  experiments  conducted  in  the  Olney  orchard  were  dupli- 
cated in  the  Tamaroa  orchard.  The  same  number  of  plats  was  used 
and  the  time  of  applying  the  various  treatments  was  practically  the 
same.  Bitter  rot  first  appeared  in  this  orchard  July  6th,  but,  as  in 
the  Olney  orchard,  it  proved  to  be  so  scarce  as  to  make  the  results 
absolutely  inconclusive  and  unreliable.  The  crop,  too,  was  so  light 
and  scattering  as  to  interfere  with  the  work  very  materially.  The 
data  gathered  are  summarized  in  Table  10,  p.  504. 


502 


BULLETIN  No.  117. 


[August, 


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ORCHARD  OF  J.  W.  HEATON,  NEW  BURNSIDE,  JOHNSON  COUNTY, 

1903 

Experiments  in  the  New  Burnside  orchard  were  not  begun  until 
after  the  owner  had  applied  the  early  sprayings  for  apple  scab  and 
codling  moth.  The  block  of  trees  used  was  of  the  Ben  Davis  variety. 
The  trees  were  divided  into  three  plats  of  ten  trees  each.  Rot  was 
discovered  June  25th  on  an  Early  Harvest  tree  but  did  not  occur 
on  the  Ben  Davis  variety  until  September  7th.  The  windfalls  were 
gathered  and  examined  September  7th,  :8th,  and  October  6th.  The 
fruit  was  picked  from  the  trees  and  the  records  completed  October 
6th.  The  plats  were  treated  as  follows : 

Plat  I — Check  plat,  received  only  the  early  sprayings  for  apple 
scab  and  codling  moth. 

Plat  II — Sprayed  once  with  Bordeaux  mixture,  June  24tli,  be- 
fore the  disease  appeared,  in  addition  to  the  early  spraying  for  scab 
and  codling  moth. 

Plat  III — Sprayed  once  with  Bordeaux  mixture  after  the  disease 
appeared,  in  addition  to  the  early  treatment  for  scab  and  codling 
moth. 

In  this  orchard  again  very  little  bitter  rot  appeared  and  the  re- 
sults from  all  plats  were  so  similar  as  to  afford  no  conclusive  data. 

Table  1 1  gives  the  data  recorded  in  the  New  Burnside  orchard. 

ORCHARD  OE  CHARLES  ALLEN,  CARBONDALE,  JACKSON  COUNTY, 

1903 

This  orchard,  like  the  one  at  New  Burnside,  was  secured  after 
the  early  sprayings  for  apple  scab  and  codling  moth  had  been  com- 
pleted. Three  plats  of  ten  trees  each  were  laid  out  in  a  block  of 
Ben  Davis  trees.  The  treatment  of  the  plats  was  as  follows : 

Plat  I — Received  only  the  early  applications  for  apple  scab  and 
codling  moth. 

Plat  II — Sprayed  once  with  Bordeaux  mixture,  June  27th,  be- 
fore bitter  rot  appeared  in  addition  to  the  early  sprayings  for  apple 
scab  and  codling  moth. 

Plat  III — Sprayed  once  with  Bordeaux  mixture,  August  I7th, 
after  the  disease  appeared. 

Bitter  rot  was  first  discovered  on  August  I7th,  the  date  of  the 
spraying  of  Plat  III.  The  fallen  apples  were  gathered  September 
5th  and  I9th,  and  the  crop  was  picked  from  the  trees  on  the  lat- 
ter date. 

Here  again  the  amount  of  bitter  rot  was  small,  though  slightly 
greater  than  in  the  Olney,  Tamaroa,  and  New  Burnside  orchards. 
It  would  not  be  safe  to  draw  conclusions  from  the  results  of  this 
experiment  but  there  is  a  pretty  strong  indication  that  one  spraying 


506 


BULLETIN  No.  117. 


[August, 


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either  shortly  before  or  im- 
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of  the  disease  is  entirely  in- 
effectual in  controlling  the  dis- 
ease. 

The  results  of  the  experi- 
ment in  the  Charles  Allen  orch- 
ard are  given  in  Table  12. 

ORCHARD   OF    H.    E.    ALLEN, 

CARBONDALE,  JACKSON 

COUNTY,  1903 

The  only  orchard  to  furnish 
decisive  data  during  the  season 
of  1903  was  that  of  Mr.  H.  E. 
Allen,  near  Carbondale.  Bitter 
rot  developed  severely  in  this 
orchard  and  some  valuable  in- 
formation was  obtained  through 
the  experiments  conducted 
therein.  The  block  of  trees  in 
this  orchard  consisted  of  Jona- 
than, Winesap,  and  Ben  Davis 
vareties.  Spraying  for  scab 
and  codling  moth  had  been  ac- 
complished before  the  Depart- 
ment began  work.  Three  plats 
of  ten  trees  each  were  laid  out, 
each  plat  containing  several 
trees  of  each  variety  mentioned 
above.  The  plats  received  ap- 
plications of  spray  as  follows, 
p.  509. 


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DIAGRAM  OF  PLATS  IN  THE  ORCHARD  OF  J.  W.  HEATON,  NEW  BURNSIDE,  1903 


508 


BULLETIN  No.  117. 


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the  early  sprayings  for  scab 
and  bitter  rot. 

Plat  II — Sprayed  with 
Bordeaux  mixture  for  bitter 
rot,  June  26th  and  July  ist, 
before  the  disease  appeared. 
Plat  III — Sprayed  twice 
with  Bordeaux  mixture  for 
bitter  rot  after  the  disease 
appeared,  /.  e.,  August  5th 
and  6th. 

Bitter  rot  first  appeared 
August  5th.  Records  were 
made  on  the  fallen  apples 
August  1 5th,  1 7th,  28th, 
September  5th  and  i8th. 
The  Jonathans  were  picked 
from  the  trees  September 
5th  and  the  Ben  Davis  and 
Winesaps  September  2ist. 
In  Table  13  the  different 
varieties  are  given  sepa- 
rately. 

In  order  that  the  compar- 
isons between  the  treatments 
may  be  made  more  readily, 
the  percentages  of  the  fruit 
liable  to  bitter  rot  saved  by 
the  early  spraying  as  com- 
pared with  the  late  spraying 
and  check  plats  are  given  in 
Table  14,  p.  511. 


510 


BULLETIN  No.  117. 


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1907.]      BITTER  ROT  OF  APPLES,  HORTICULTURAL  INVESTIGATIONS.     511 


TABLE  14.— SAVING  EFFECTED  BY  Two  EARLY  SPRAYINGS  FOR  BITTER 
ROT  OVER  OTHER  PLATS  IN  ORCHARD  OF  MR.  H.  E.  ALLEN 


No.  of 
plat. 

Treatment. 

Saving 
over 
plat  III. 

Saving 
over 
check 
I. 

Jonathan 

II 

Sprayed  twice 
appeared  .  . 

for  bitter  rot  before  disease 

67.19 

60.71 

Winesap 

II 

Sprayed  twice 
appeared  .  . 

for  bitter  rot  before  disease 

35  47 

69.44 

Ben  Davis 

II 

Sprayed  twice 
appeared  . 

for  bitter  rot  before  disease 

57.60 

49.39 

A  study  of  the  two  preceding  tables  shows  at  once  the  severely 
infected  character  of  the  fruit  in  this  orchard,  as  much  as  75  percent 
of  the  crop  being  infected  in  some  of  the  plats.  The  Winesap  va- 
riety proved  to  be  less  subject  to  the  disease  than  the  Jonathan  and 
Ben  Davis,  each  of  these  two  kinds  being  about  equally  attacked  by 
bitter  rot.  None  of  the  treatments  given  was  wholly  successful  in 
combating  the  disease.  In  fact,  in  the  case  of  Jonathan  and  Ben 
Davis  apples,  the  crop  on  the  plats  sprayed  after  the  appearance  of 
the  rot  showed  a  higher  percentage  of  diseased  fruit  than  that  on 
the  check  plat.  In  both  cases  the  infection  is  so  much  higher  as  to 
kad  to  a  suspicion  that  the  operation  of  spraying  had  aided .  in 
spreading  the  disease  rather  than  in  suppressing  it,  though  it  is  pos- 
sible that  there  may  have  been  enough  more  sources  of  infection 
among  some  of  the  trees  in  the  late  sprayed  plats  to  account  for 
the  difference.  In  the  Winesap  plat,  however,  the  late  spraying 
appeared  to  reduce  the  rot  considerably,  and  hence  it  would  hardly 
be  safe  to  assume  that  the  bitter  rot  was  disseminated  in  any  degree 
by  the  spray  applied  to  the  late  sprayed  Jonathan  and  Ben  Davis 
trees.  Very  marked  and  encouraging  results  were  obtained  by  the 
two  sprayings  with  Bordeaux  mixture  shortly  before  the  appearance 
of  the  rot,  60.71  percent  of  all  the  Jonathans  liable  to  attack,  as 
shown  by  the  infection  of  the  check  plat,  69.44  percent  of  the  Wine- 
saps,  and  49.39  percent  of  the  Ben  Davis  being  saved  by  these  two 
applications.  These  results  corroborate  in  a  very  significant  man- 
ner those  obtained  in  1902  in  the  Tonti  orchard  where  the  plats 
sprayed  a  number  of  times  before  the  appearance  of  the  disease 
showed  a  better  degree  of  control  than  those  sprayed  later. 


512  BULLETIN  No.  117.  [August, 

CONCLUSIONS  FOR  1903 

This  year's  work  proved  so  inconclusive  in  all  the  orchards,  ex- 
cept that  of  Mr.  H.  E.  Allen  of  Carbondale,  that  the  results  are 
not  brought  together  into  one  tabulation  as  was  done  with  the  re- 
sults of  the  work  in  1902.  The  following  points  are  the  only  ones 
that  seem  to  warrant  the  making  of  definite  statements. 

1.  Spraying  with  Bordeaux  mixture  before  the  appearance  of 
the  disease  again  proved  more  effective  in  combating  the  disease 
than  spraying  after  the  infection  had  occurred. 

2.  One  spraying  either  before  or  after  the  appearance  of  the  rot 
did  not  appreciably  reduce  the  destructiveness  of  the  disease. 

3.  Two  sprayings  before  the  appearance  of  the  rot  were  insuf- 
ficient to  control  the  disease  completely  but  did  reduce  it  by  about 
one-half. 

4.  To  prevent  the  damage  which  may  be  caused  by  bitter  rot,  it 
is  necessary  to  have  the  fruit  thoroughly  coated  with  Bordeaux 
mixture  before  the  disease  breaks  out. 

The  following  problems,  the  solutions  of  which  were  undertaken 
in  1903,  were  left  unsolved  or  partially  so : 

1.  Will  spraying  dormant  wood  in  the  fall  with  copper  sulphate 
solution  prevent  the  disease  ? 

2.  Will  spraying  dormant  wood  in  the  spring  with  copper  sul- 
phate solution  prevent  the  disease  ? 

3.  Will  spraying  three  times  in  July  with  Bordeaux  mixture 
prevent  the  disease? 

4.  Will  spraying  with  Bordeaux  mixture  at  intervals  of  ten  days 
after  the  first  three  sprayings  until  after  July  ist  prevent  the  diss 
ease? 

1904 

Experiments  were  continued  in  the  Flora,  Olney,  and  Tamaroa 
orchards  and  installed  in  an  orchard  near  Kell  during  the  season  of 
1904.  This  season  proved  again  unfavorable  to  the  development 
of  the  disease,  its  distribution  over  the  state  and  among  the  plats 
and  trees  in  individual  orchards  being  most  uneven.  As  in  the  pre- 
ceding season  only  one  orchard,  that  near  Kell,  gave  uniform  re- 
sults and  evidenced  anything  like  a  uniform  infection  of  the  rot. 
The  same  plan  of  experiments  was  followed  as  in  1903,  except  in 
the  case  of  Plat  I,  where  the  fall  treatment  using  copper  sulphate 
solution  on  the  dormant  wood  was  replaced  with  a  treatment  using 
Oregon  Wash  applied  to  the  dormant  wood  in  the  spring. 


1907.}     BITTER  ROT  OF  APPLES,  HORTICULTURAL  INVESTIGATIONS.      513 

ORCHARD  OF  DALE  MANN,  FLORA,  CLAY  COUNTY,  1904 

Nine  plats  consisting  mostly  of  trees  of  the  Willow  Twig  variety 
were  laid  out  in  an  orchard  at  Flora.  The  plats  comprised  from  ten 
to  fifteen  trees  each,  in  all,  one  hundred  and  twenty-five  trees.  The 
orchard  was  sprayed  three  times  early  in  the  season  for  apple  scab, 
codling  moth,  and  canker  worm,  the  applications  being  made  April 
1 6th,  May  I3th,  and  May  2oth.  All  plats  received  these  three  spray- 
ings, and  the  treatments  given  subsequently  were  as  follows : 

Plat  I — Sprayed  March  29th  with  Oregon  Wash. 

Plat  II — Sprayed  March  29th  with  copper  sulphate  solution,  one 
pound  of  copper  sulphate  to  fifteen  gallons  of  water. 

Plat  III — Check  plat,  no  applications  made  after  the. three  early 
sprayings  above  referred  to. 

Plat  IV — Sprayed  with  Bordeaux-Paris  green  mixture  three 
times  at  intervals  of  ten  days  beginning  on  or  about  July  ist.  The 
applications  were  made  July  9th,  I9th,  and  29th. 

Plat  V. — Sprayed  with  Bordeaux  mixture  about  every  ten  days 
after  the  early  spraying  for  apple  scab  and  codling  moth,  until 
after  July  ist.  The  applications  were  made  May  3Oth,  June  8th, 
2Oth,  29th,  and  July  9th. 

Plat  VI — Sprayed  four  times  with  Bordeaux  mixture  as  fol- 
lows:  June  8th,  I5th,  2oth,  and  29th. 

Plat  VII — Check  plat,  no  applications  made  after  the  three  early 
sprayings  above  referred  to. 

Plat  VIII — Sprayed  when  bitter  rot  first  appeared  until  the  fruit 
was  thoroughly  coated  with  Bordeaux  mixture. 

Plat  IX — Check  plat,  no  applications  made  after  the  three  early 
sprayings  above  referred  to. 

The  fallen  apples  were  gathered  August  loth,  29th,  Septem- 
ber 8th,  3 ist,  and  October  28th,  and  the  fruit  was  picked  from  the 
trees  on  the  date  last  mentioned,  October  28th.  The  data  are  found 
in  Table  15. 

The  amount  of  bitter  rot  on  the  various  check  plats  was  very  in- 
constant, Plat  III  having  only  1.87  percent  and  Plats  VII  and  IX 
having  19.28  percent  and  5.70  percent,  respectively.  Plat  III,  how- 
ever, produced  only  a  very  light  crop  of  apples  as  compared  with 
Plats  VII  and  IX  and  appears  to  have  been  under  exceptional  condi- 
tions. Comparing  the  sprayed  plats  with  check  Plats  VII  and  IX 
there  is  a  marked  advantage  in  favor  of  all  the  treated  plats.  No  one 
of  the  treated  plats  showed  any  marked  superiority  over  the  others, 
but  the  plat  sprayed  with  Oregon  Wash  on  dormant  wood  in  the 
spring  showed  a  much  higher  percentage  of  bitter  rot  than  did  any 
other  of  the  treated  plats,  and  almost  as  high  a  percentage  as  check 
Plat  IX.  Owing,  however,  to  the  irregularity  of  the  results  in  the 
check  plats  it  seems  unsafe  to  say  just  how  much  of  the  apparent 


514 


BULLETIN  No.  117. 


[August, 


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BITTER  ROT  OF  APPLES,  HORTICULTURAL  INVESTIGATIONS.      515 


0  Willow.Twig  0  Rome  Beauty  yy  -<•  •  ©  Maiden  Blush  0  Unknown 
Q  Ben  Davis  £  Grimes  Golden 
DIAGRAM  OF  PLATS  IN  THE  ORCHARD  OF  DALE  MANN,  FLORA,  1904-05 

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516  BULLETIN  No.  117. 

protection  afforded  the  treated  plats  was  due  to  spray  and  how 
much  was  due  to  advantages  in  circumstances  of  infection.  The  re- 
sults of  the  experiment  are,  therefore,  suggestive  rather  than  con- 
clusive. 

ORCHARD  OF  J.  L.  ZOOK,  OLNEY,  RICHLAND  COUNTY,  1904 

The  experimental  plats  in  this  orchard  consisted,  as  in  the  case 
of  the  Flora  orchard,  of  nine  plats  of  fifteen  trees  each.  (For  plan 
of  plats  see  p.  503.)  The  variety  was  Ben  Davis  and  the  treat- 
ments given  each  plat  were  identical  with  those  given  in  the  Flora 
orchard.  Bitter  rot  appeared  in  this  orchard  July  2/th.  Rec- 
ords were  made  on  the  fallen  apples  on  July  I2th,  August  I2th, 
i/th,  26th,  September  7th,  I5th,  24th,  3Oth,  and  October  2oth. 
The  crop  was  picked  from  the  trees  October  2Oth  and  2ist  and 
the  data  compiled  in  Table  16,  p.  517. 

None  of  the  plats  in  this  orchard  showed  any  serious  develop- 
ment of  the  disease.  The  percentage  of  bitter  rot,  however,  runs 
uniformly  less  throughout  all  plats  sprayed  with  Bordeaux  mixture 
than  through  the  check  plats  and  the  plats  which  were  treated  with 
Oregon  Wash  and  copper  sulphate  on  the  dormant  wood  early  in 
the  spring.  Here  again  the  results  are  suggestive,  but  not  marked 
enough  to  be  conclusive. 

ORCHARD  OF  F.  L.  WILLIAMS  &  SON,  TAMAROA,  PERRY  COUNTY, 

1904 

In  this  orchard  the  same  schedule  of  treatments  was  given  as  in 
the  Flora  and  Olney  orchards,  except  in  the  case  of  Plat  IX,  which ' 
was  sprayed  with  Bordeaux  mixture  until  the  fruit  was  thoroughly 
coated  after  the  rot  had  become  well  established.  (For  plan  of  plats 
see  p.  503.)  The  dates  of  spraying  were  nearly  the  same,  varying 
only  a  day  or  so  for  corresponding  applications.  The  check  plats 
consisted  of  ten  trees  each  and  all  other  plats  of  fifteen  trees  each. 
The  variety  was  Ben  Davis.  Bitter  rot  first  appeared  July  i6th. 
The  fallen  fruit  was  gathered  on  August  ist  and  2d,  9th  and  loth, 
I7th,  25th,  September  2d  and  3d,  I5th  and  i6th,  27th  and  28th, 
and  October  26th  and  3ist.  The  crop  was  picked  from  the  trees 
October  27th,  28th,  and  29th.  The  data  secured  are  tabulated  in 
Table  17,  p.  518. 


1007.]      BITTER  ROT  OF  APPLES,  HORTICULTURAL,  INVESTIGATIONS.     517 


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1907. ]     BITTER  ROT  OF  APPLES,  HORTICULTURAL,  INVESTIGATIONS.      519 

The  data  contained  in  Table  17  are  certainly  confusing.  The 
treatment  with  Oregon  Wash,  which  in  all  other  experiments 
had  proven  ineffective,  appeared  the  most  effective  of  any  of  the 
sprays  applied.  In  the  other  plats  spraying  with  Bordeaux  mixture 
seemed  to  have  only  very  slight  effects  upon  the  rot,  the  differences 
between  the  sprayed  and  the  check  plats  being  too  small  to  warrant 
the  drawing  of  any  conclusions. 

ORCHARD  OP  W.  T.  STORMENT,  KELL,  MARION  COUNTY,  1904 

Nine  plats  of  Ben  Davis  trees  were  selected  in  this  orchard,  each 
comprised  of  from  eight  to  sixteen  trees,  most  of  them  containing 
the  latter  number.  The  treatment  was  exactly  similar  to  that  given 
in  the  Williams  orchard  at  Tamaroa,  but  late  in  the  season  two  other 
plats  were  added  to  the  experiment,  these  being  designated  Plats  X 
and  XI,  and  were  treated  as  follows : 

Plat  X — Sprayed  on  July  29th  with  a  solution  of  eight  ounces  of 
copper  sulphate  to  fifty  gallons  of  water. 

Plat  XI — Sprayed  on  July  29th  with  a  solution  of  ten  ounces  of 
copper  sulphate  to  fifty  gallons  of  water. 

Bitter  rot  was  first  observed  in  the  plats  of  July  22d.  The  wind- 
falls were  gathered  July  3Oth,  August  8th,  I3th,  24th,  September 
ist,  8th,  22d,  and  October  3d.  The  fruit  was  harvested  from  Octo- 
ber 3d  to  7th.  The  results  were  then  tabulated  in  Table  1 8. 

The  most  striking  results  of  the  season  were  secured  in  the  orch- 
ard at  Kell,  but  unfortunately  the  infection  was  light  in  the  center 
of  the  orchard  where  plats  V,  VI,  and  VII  were  located,  and  the 
results  possibly  show  a  greater  saving  than  would  actually  have  oc- 
curred had  the  conditions  of  infection  been  different.  However,  the 
differences  between  the  various  treatments  are  sufficiently  wide  to 
warrant  the  drawing  of  some  definite  conclusions.  In  every  instance 
spraying  before  the  bitter  rot  appeared,  Plats  IV,  V,  and  VI,  gave 
almost  perfect  control  of  the  disease;  spraying  after  rot  appeared 
greatly  reduced  the  number  of  infected  fruits  but  did  not  control  the 
disease  so  perfectly  as  did  the  early  spraying ;  treatment  of  the  dor- 
mant wood  gave  no  beneficial  results  as  compared  with  the  check 
plats,  and  a  similar  result  followed  the  treatments  with  various 
strengths  of  copper  sulphate  solution  which  were  given  July  29th  to 
Plats  X  and  XI.  Indeed  the  application  of  the  pure  copper  sulphate 
caused  considerable  foliage  injury  and  could  not  have  been  recom- 
mended even  had  the  treatment  been  effective  in  controlling  the 
disease. 

As  corroborative  evidence  the  results  of  the  work  in  the  Kell 
orchard  are  most  valuable.  It  will  be  remembered  that  all  the  data 
thus  far  obtained  point  strongly  to  the  advisability  of  coating  the 
fruit  thoroughly  with  Bordeaux  mixture  before  the  first  occurrence 
of  bitter  rot,  as  the  safest  and  surest  preventive  of  the  disease.  More- 


520 


BULLETIN  No.  117. 


[August, 


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1907.}      BITTER  ROT  OF  APPLES,  HORTICULTURAL  INVESTIGATIONS.     521 


over  it  strongly  corroborated  the  data  showing  the  ineffectiveness 
of  treatments  of  the  dormant  wood  with  Oregon  Wash  and  copper 
sulphate  solution,  obtained  in  the  Flora  and  Olney  orchards,  and 
indicates  that  the  low  percentage  of  bitter  rot  appearing  in  the  Wil- 
liams orchard  at  Tamaroa  on  the  plat  treated  with  Oregon  Wash 
was  due  rather  to  lighter  infection  or  to  some  other  cause  than  to 
the  treatment  itself. 

The  following  table  shows  the  percentage  saving  of  the  total 
amount  of  infection,  as  shown  by  the  check  plats,  of  the  various 
treatments  over  the  checks.  The  average  of  the  two  check  plats, 
III  and  VII,  is  taken  as  the  standard  of  infection,  though  as  a  mat- 
ter of  fact  higher  infections  appeared  in  three  other  plats,  those  in 
which  the  dormant  wood  was  treated  with  Oregon  Wash  and  cop- 
per sulphate  solution,  Plats  I  and  II,  and  the  plat  which  was  sprayed 
with  pure  copper  sulphate  solution  on  July  29th,  Plat  X. 


TABLE  19 


-SAVING  EFFECTED  BY  VARIOUS  TREATMENTS  IN  THE  KELL 
ORCHARD,  1904 


No.  of 
plat. 

Treatment. 

Saving 
over 
check 
plats. 

IV 

Sprayed  three  times  in  July  at  intervals  of  ten   days 
with  Bordeaux-Paris  green  mixture  

.    Per- 
centag-e 
94  59 

V 

Sprayed  at  intervals  of  ten  days  until  after  July  1st  with 
Bordeaux-Paris  green  mixture  

98.20 

VI 

Sprayed  once  each  week  during  June   with  Bordeaux- 
Paris  green  mixture  

95.42 

VIII 

Sprayed  with  Bordeaux-Paris  green  mixture  until  fruit 
was  thoroughly  coated  after  rot  first  appeared  

72.02 

IX 

Sprayed  with  Bordeaux-Paris  green  mixture  until  fruit 
was  thoroughly  coated  after  rot  had  become  established 

81.91 

From  the  above  figures  it  appears  that  spraying  with  Bordeaux 
mixture  three  to  five  times  before  ihe  appearance  of  the  rot  may 
control  from  94.59  to  98.20  percent  of  the  entire  loss  due  to  bitter 
rot. 

Since  the  treatments  in  the  various  orchards  during  the  year 
1904  are  all  similar,  and  since  in  drawing  conclusions  on  experi- 
mental work  of  any  kind  it  is  well  to  employ  the  most  available  data, 
providing  it  has  been  gathered  under  equally  good  conditions  of  con- 
trol, a  summary  of  the  results  from  the  four  orchards  under  observa- 
tion is  given  below.  For  greater  convenience  in  comparing  the  re- 
sults the  totals  of  all  the  check  plats  are  given  and  placed  at  the  head 
of  the  table ;  the  other  plats  are  numbered  as  in  the  case  of  the  tables 
preceding,  and  a  column  is  added  showing  the  percentage  gain  of 
the  various  treated  plats  in  cases  where  gains  resulted. 


522 


BULLETIN  No.  117 


[August, 


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524  BULLETIN  No.  117.  [August, 

On  account  of  the  irregular  character  of  the  infection  in  the 
Tamaroa  orchard  in  1904,  a  similar  table  has  also  been  prepared 
giving  a  summary  of  the  data  obtained  in  the  Flora,  Olney,  and 
Kell  orchards  alone,  a  table  which  the  author  believes  to  be  more 
nearly  an  expression  of  the  actual  value  of  the  spraying  operations 
than  Table  20,  referred  to  in  the  preceding  paragraphs. 

The  two  tables  are  given  on  pp.  522  and  523. 

CONCLUSIONS  FOR  1904 

1.  Treatment  of  the  dormant  wood  with  either  Oregon  Wash 
or  copper  sulphate  solution  was  entirely  ineffectual  in  controlling 
bitter  rot. 

2.  Spraying  with  Bordeaux  mixture  from  three  to  five  times  at 
various  intervals  shortly  before  the  appearance  of  the  rot  was  by  all 
means  the  most  effective  treatment  in  preventing  the  ravages  of  the 
disease,  preventing  from  41.83  percent  to  53.80  percent  of  the  entire 
loss  due  to  bitter  rot,  when  the  results  of  the  work  in  the  four  or- 
chards are  totaled.     Leaving  out  the  Tamaroa  orchard,  where  the 
infection  seemed  to  be  very  unequally  distributed  among  the  various 
plats,  as  already    explained    on    p.     519,     Plats  IV,  V,  and  VI, 
which  were  sprayed  from  three  to  five  times  before  the  appearance 
of  the  rot,  gave  the  following  percentages  of  saving  over  the  check 
plats,  respectively;   Plat  IV,  91.43  percent;   Plat  V,  95.89  percent; 
Plat  VI,  91.43  percent. 

3.  Spraying  after  the  appearance  of  the  disease  with  Bordeaux 
mixture  effected  a  saving  of  18  to  20  percent  in  all  orchards,  and  of 
52  to  63  percent  in  the  three  orchards  at  Flora,  Olney,  and  Kell- 

1905 

In  1905  it  was  decided,  on  account  of  the  scarcity  of  bitter  rot 
the  year  before,  to  abandon  work  in  the  Olney  and  Tamaroa  orch- 
ards, selecting  instead  orchards  that  had  a  good  crop  with  a  plentiful 
supply  of  bitter  rot  the  preceding  year.  The  Mann  orchard  at  Flora 
and  the  orchard  of  Mr.  John  Blackledge,  of  Clay  City,  were  chosen 
for  the  purpose,  and  additional  lines  of  inquiry  were  involved  in  the 
experiments  for  this  season  as  follows:  (i)  the  application  of 
twenty-five  pounds  of  salt  on  the  ground  under  each  tree  of  a  plat ; 
(2)  spraying  a  plat  with  soluble  Bordeaux  mixture  once  each  week 
during  June;  (3)  spraying  once  only  during  early  treatment  for 
scab  and  codling  moth;  (4)  spraying  with  dust  spray;  (5)  spray- 
ing at  intervals  of  ten  clays  after  the  early  sprayings  for  scab  and 
codling  moth  with  copper  sulphate  solutions  of  varying  strengths ; 
(6)  omitting  the  early  sprayings  for  scab  and  codling  moth  entirely. 

ORCHARD  OF  DALE  MANN,  FLORA,  CLAY  COUNTY,  1905 

Nine  plats  were  laid  out  in  a  block  of  .Willow  Twig  apples, 
seven  plats  consisting  of  fifteen  trees  each,  and  two  plats,  those  re- 


1907.]     BITTER  ROT  OF  APPLES,  HORTICULTURAL  INVESTIGATIONS.      525 

served  as  checks  and  given  no  treatment,  of  ten  trees  each,  or,  in 
all,  one  hundred  and  twenty-five  trees.  All  of  the  plats  received  the 
first  and  third  applications  for  scab  and  codling  moth,  the  first  spray- 
ing being  given  April  4th  and  5th,  before  the  blossoms  opened,  and 
the  second  May  8th,  one  week  after  the  petals  had  fallen.  The 
treatment  for  bitter  rot  consisted  of  .applications  of  Bordeaux-Paris 
green  mixture  made  up  according  to  the  standard  formula,  the  same 
as  used  in  previous  seasons,  four  pounds  of  lime,  four  pounds  cop- 
per sulphate,  four  ounces  of  Paris  green,  and  fifty  gallons  of  water. 
The  exact  treatment  of  each  of  the  plats  for  bitter  rot,  that  is  the 
treatment  following  the  two  early  sprayings  for  scab  and  codling 
moth,  was  as  follows : 

Plat  I — Treated  with  25  pounds  salt  distributed  about  each  tree, 
May  27th. 

Plat  II — Sprayed  with  soluble  Bordeaux  June  6th,  I3th,  2Oth 
and  27th*. 

Plat  III- — Not  sprayed  for  bitter  rot. 

Plat  IV — Sprayed  with  Bordeaux- Paris  green  mixture  July  6th, 
1 5th,  and  25th. 

Plat  V — Sprayed  with  Bordeaux-Paris  green  mixture  May  18, 
June  6th,  I5th,  and  27th. 

Plat  VI — Sprayed  with  Bordeaux-Paris  green  mixture  June 
6th,  1 3th,  2oth,  and  27th. 

Plat  VII — Not  sprayed  for  bitter  rot. 

Plat  VIII — Sprayed  with  Bordeaux-Paris  green  mixture  three 
times,  July  25th,  when  bitter  rot  was  first  discovered. 

Plat  IX — Not  sprayed  for  bitter  rot. 

^Preparation  of  Soluble  Bordeaux  Mixture — The  Soluble  Bordeaux  mix- 
ture used  in  this  experiment  was  prepared  according-  to  a  formula  obtained 
from  Professor  S.  M.  Babcock  of  the  University  of  Wisconsin,  as  follows: 

STOCK  SOLUTIONS 

1  -  Copper  Sulphate  Solution: 

Dissolve  1  pound  of  copper  sulphate  in  2  gallons  of  cold  water, 

2 — Solution  of  sucrate  of  lime: 

Slake  10  pounds  of  fresh  lime  through  a  wire  strainer  and  add  a  solution 
of  25  pounds  of  granulated  sugar  in  SO  pounds  of  water.  Stir  thoroughly  at 
frequent  intervals,  and  after  two  or  three  hours  decant  or  siphon  the  clear 
liquid  from  the  undissolved  lime. 

The  quantities  named  are  sufficient  for  about  8  gallons  of  standard  solu- 
tion of  sucrate  of  lime. 

SPRAYING  SOLUTION 

Take  equal  parts  of  solutions  1  and  2  and  add  three  parts  of  water.  Agi- 
tate until  the  copper  hydrate,  which  is  at  first  precipitated,  is  entirely  dis- 
solved. Upon  standing  a  slight  deposit  of  gypsum  is  formed  leaving  a 
deep  blu-^  solution  of  hydrate  of  copper.  If  desired  the  spray  may  be  applied 
immediately  after  preparation  as  the  small  amount  of  finely  divided  gypsum 
will  not  interfere  with  the  operation.  Prepared  in  this  manner  the  solution 
contains  about  the  same  amount  of  copper  hydrate  as  the  ordinary  Bordeaux 
mixture.  It  may  be  diluted  indefinitely  with  water  without  a  precipitate 
forming. 


526 


BULLETIN  No.  117. 


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1907.  |      BITTER  ROT  OF  APPLES,  HORTICULTURAL,  INVESTIGATIONS.     527 


(For  plan  of  plats  see  p.  515).    . 

Bitter  rot  was  first  discovered  in  these  plats  on  July  25th.  The 
fallen  apples  were  gathered  and  recorded  August  5th,  i6th,  2ist, 
September  8th,  22d,  and  October  4th  and  5th.  On  the  latter  date 
the  crop  remaining  upon  the  trees  was  harvested,  and  the  data  tabu- 
lated below  give  the  results  of  the  experiments. 

-The  results  of  the  experiment  in  the  Flora  orchard  are  strikingly 
in  accord  with  the  results  obtained  in  the  Flora,  Olney,  and  Kell 
orchards  in  1904.  Plat  IV  which  received  three  sprayings  during 
July,  or  as  near  to  the  time  of  the  first  appearance  of  the  bitter  rot  as 
they  could  be  applied  in  accordance  with  a  plan  of  spraying  at  inter- 
vals of  ten  days,  gave  a  very  perfect  degree  of  control  of  the  disease, 
and  proved  somewhat  more  effective  than  spraying  either  during" 
June  or  after  the  appearance  of  the  rot.  Spraying  both  in  June  and 
after  the  appearance  of  the  rot,  had  a  decidedly  beneficial  effect  in 
preventing  the  disease.  The  treatment  of  the  ground  with  salt  pro- 
duced no  apparent  diminution  in  the  infection.  In  fact  more  bitter 
rot  was  found  in  that  plat  than  in  the  average  of  the  three  check 
plats.  The  accompanying  table  shows  the  relative  saving  effected  by 
the  various  treatments  over  the  average  of  the  check  plats. 

TABLE  23.— PERCENTAGE  SAVING  SHOWN  BY  THE  TREATED  PLATS  OVER 

THE  CHECK  PLATS 


No.  of 

plat. 

Treatment. 

Percentage 
gain  over 
.average 
check  plat. 

I 

Ground  treated  with  twenty-five  pounds  of  salt  per 
tree  

None 

II 

Sprayed  once  each  week  during  June  with  soluble 
Bordeaux  mixture  

78.06 

IV 

Sprayed  three  times  at  intervals  of  ten  days  during 
July  with  Bordeaux-Paris  green  mixture  

92.14 

V 

Sprayed  at  intervals  of  ten  days  until  July  1st  with 
Bordeaux-  Paris  green  mixture  .  .  . 

81.00 

VI 

Sprayed  once  each  week  during  June  with  Bordeaux- 
Paris  green  mixture  

68.42 

VIII 

Sprayed  with  Bordeaux-Paris  green  until  fruit  was 
thoroughly  coated  when  disease  first  appeared  .  . 

71.63 

The  figures  given  in  the  above  tabulation  indicate  very  clearly 
the  high  degree  of  benefit  derived  from  all  the  different  forms  of 
spraying  employed  in  the  experiment  and  corroborate  the  results  of 
previous  years  in  which  from  70  to  90  percent  of  all  the  fruit  liable 
to  bitter  rot  was  saved  by  spraying  with  Bordeaux  mixture. 


528  BULLETIN  No.  117.  [Awjust, 

ORCHARD  OF  JOHN  BLACKI^DGE;,  CLAY  CITY,  CLAY  COUNTY,  1905 

A  very  comprehensive  series  of  eighteen  plats  was  selected  in 
the  Ben  Davis  orchard  of  Mr.  Blackledge,  of  Clay  City,  in  1905. 
There  was  a  promise  of  a  good  set  of  fruit  and  bitter  rot  had  been 
prevalent  the  previous  year.  Hence  it  was  hoped  that  some  valuable 
data  might  be  obtained  in  this  orchard.  Most  of  the  plats  received 
the  first  three  sprayings  for  apple  scab  and  codling  moth  with  Bor- 
deaux-Paris green  mixture  made  up  according  to  the  standard  form- 
ula. Plats  XIII  and  XVI,  however,  were  sprayed  with  the  dust 
Bordeaux-Paris  green  preparation,  Plats  VII  and  XVIII  received 
the  first  early  spray  only,  while  Plats  XI  and  XIV  were  not  sprayed 
at  any  time  during  the  season.  The  early  treatments  were  given 
April  nth  to  I4th,  April  28th  and  29th,  and  May  5th  to  9th.  The 
schedule  of  treatments  planned  for  each  plat  was  as  follows : 

Plat  I — Salt,  one  application;  twenty-five  pounds  to  each  tree 
evenly  spread  on  the  ground. 

Plat  II — To  be  sprayed  three  times  at  intervals  of  about  ten 
days  beginning  about  July  1st  using  Bordeaux-Paris  green  mixture. 

Plat  III — Check,  to  receive  no  spray  after  first  three  applications. 

Plat  IV — Commencing  after  third  early  application  to  be  sprayed 
at  intervals  of  ten  days  until  after  July  ist,  using  Bordeaux-Paris 
green  mixture. 

Plat  V — To  be  sprayed  four  times  in  June,  on  or  about  the  4th, 
nth,  i8th,  and  25th,  using  Bordeaux- Paris  green  mixture. 

Plat  VI — To  be  sprayed  until  the  fruit  was  thoroughly  coated 
as  soon  as  bitter  rot  first  appeared  with  Bordeaux-Paris  green  mix- 
ture. 

Plat  VII — Check,  to  receive  no  spray  whatever  after  the  first 
three  applications. 

Plat  VIII — To  be  sprayed  until  the  fruit  was  completely  coated 
after  bitter  rot  had  become  thoroughly  established,  with  Bordeaux- 
Paris  green  mixture. 

Plat  IX — To  be  sprayed  with  copper  sulphate  solution,  three 
pounds  to  fifty  gallons  of  water.  To  be  applied  ten  days  after  third 
spraying  and  then  if  no  foliage  injury  followed  to  be  repeated  every 
ten  days. 

Plat  X — To  be  sprayed  with  copper  sulphate  solution,  six  pounds 
to  fifty  gallons  of  water.  To  be  applied  ten  days  after  third  spray- 
ing and  then  if  no  foliage  injury  followed  to  be  repeated  every 
ten  days. 

Plat  XI — Check,  to  receive  no  spray  whatever. 

Plat  XII — Liquid,  to  be  given  three  applications  of  Bordeaux- 
Paris  green  mixture  at  intervals  of  ten  days,  beginning  ten  days 
after  third  application. 


1907.']     BITTER  ROT  OP  APPLES,  HORTICULTURAL  INVESTIGATIONS.     529 

Plat  XIII — Dust,  to  be  applied  at  the  same  time  the  liquid  spray 
was  applied  to  Plat  XII. 

Plat  XIV — Check,  to  receive  no  spray  whatever. 

Plat  XV — Liquid  to  be  given  six  applications  of  Bordeaux- 
Paris  green  mixture  at  intervals  of  ten  days  beginning  ten  days 
after  the  third  spraying  for  apple  scab  and  codling  moth. 

Plat  XVI — Dust,  to  be  applied  at  the  same  time  the  liquid  spray 
was  applied  to  Plat  XV. 

Plat  XVII — To  be  treated  with  twenty-five  pounds  of  salt  to 
each  tree  but  to  receive  no  early  sprayings. 

Plat  XVIII — Check,  to  receive  no  treatment  whatever. 

Bitter  rot  was  first  noticed  July  2ist  and  occurred  rather  spas- 
modically after  every  rain  and  warm  spell  throughout  the  season. 

The  disease  varied  considerably  in  the  severity  with  which  it  at- 
tacked various  parts  of  the  orchard.  There  was  very  little  rot  on 
Plats  VIII  and  XVI  which  were  located  at  the  south  end  of  the 
orchard.  Plat  X  which  was  located  in  a  low  place  somewhat  isolated 
from  the  rest  also  showed  almost  no  infection,  and  Plat  XVII  con- 
tained only  two  trees  neither  of  which  was  much  infested.  These 
four  plats,  then,  are  left  out  in  the  tabulation  of  data  which  follows. 
Windfalls  were  gathered  July  7th  to  I3th,  August  yi  to  7th,  i6th 
to  i  Qth,  24th  and  25th,  September  ist  to  4th,  7th  and  8th  and  2Oth 
to  22d.  The  crop  was  harvested  September  25th  to  October  3d, 
and  the  records  completed  as  follows,  Table  24. 

In  this  orchard  again  plats  sprayed  several  times  just  previous 
to  the  discovery  of  the  disease  showed  very  much  less  bitter  rot  than 
the  other  plats.  Spraying  until  the  fruit  was  thoroughly  coated  with 
Bordeaux  mixture  either  as  soon  as  the  disease  was  discovered  or 
after  it  had  become  thoroughly  established  proved  much  less  effect- 
ive in  combating  it  than  did  the  same  treatment  in  the  Flora  orchard. 
Spraying  with  pure  copper  sulphate  solution  gave  no  decisive  results. 
In  fact  there  was  a  larger  infection  of  the  disease  in  Plat  IX,  which 
was  treated  with  three  pounds  of  copper  sulphate  to  fifty  gallons  of 
water,  than  in  some  of  the  check  plats.  Dust  spraying  proved  very 
unsatisfactory.  The  highest  infection  occurring  in  any  plat  was 
shown  by  Plat  XIII,  which  was  sprayed  three  times  after  the  early 
sprayings  with  dust  Bordeaux-Paris  green  mixture.  The  three 
early  sprayings  with  ordinary  Bordeaux  mixture  for  scab  and  cod- 
ling moth  appear  to  have  exercised  a  very  considerable  degree  of 
control  over  bitter  rot.  In  the  check  plats  which  received  only  the 
three  early  treatments  the  average  amount  of  the  total  crop  affected 
was  10.86  percent,  whereas,  in  the  plats  which  were  not  sprayed  at 
all  during  the  entire  season,  the  average  amount  was  35.59  percent, 
or  nearly  three  and  one-half  times  as  much.  Plat  XVIII  which  was 
sprayed  only  once  during  the  entire  season  showed  a  percentage  of 
22.17  percent  affected  by  bitter  rot,  an  amount  intermediate  between 


530 


BULLETIN  No.  117. 


[August, 


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1907.]      BITTER  ROT  OF  APPLES,  HORTICULTURAL  INVESTIGATIONS.     531 


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532 


BULLETIN  No.  117. 


[August, 


the  plats  treated  three  times  early  and  those  not  treated  at  all.  The 
following  tabulation  shows  the  percentage  gain  of  various  plats 
over  the  check  plats,  untreated  plats,  and  dust  sprayed  plats,  etc. 
The  standards  taken  in  the  case  of  the  check  plats  receiving  the  three 
early  applications  of  spray  for  the  scab  and  codling  moth  are  de- 
rived from  the  totals  of  the  two  plats,  respectively,  in  each  case,  viz., 
the  totals  of  the  two  Plats  III  and  VII  in  the  first  case,  and  Plats 
XI  and  XIV  in  the  second  case.  Plat  XIII  is  taken  as  the  dust- 
sprayed  standard. 

TABLE  25. — PERCENTAGE  GAINS  OF  VARIOUS  TREATED  PLATS  OVER  UN- 
TREATED AND  DUST  SPRAYED  PLATS  IN  THE  CLAY  CITY  ORCHARD 
IN  1905 


No.  of 
plat. 

Treatment. 

Percent- 
age gain 
over 
early 
sprayed 
plats. 

Percent- 
age gain 
over  un- 
treated 
plats. 

Percent- 
age gain 
over 
dust 
sprayed 
plats. 

I 
II 

Not  sprayed  for  rot  but  treated  with  salt 

Sprayed  three  times  at  intervals  of  ten 
days  in  July  with  Bordeaux-Paris  green 
mixture         

44.11 

61  88 

82.94 
88  37 

88.50 
92  16 

IV 

Sprayed  at  intervals  of  ten  days  until 
after  July  1  with  Bordeaux-Paris  green 
mixture  

67.40 

90.05 

93.29 

V 
VI 
IX 

Sprayed  once  each   week  during  June 
with  Bordeaux-Paris  green  mixture.  .  . 

Sprayed    until    fruit     was    thoroughly 
coated  when  bitter  rot  first  appeared 

Sprayed  twice  with  weak    copper  sul- 
phate solution  at  intervals  of  ten  days 

6.63 
18.69 

71.51 

75.19 
63  95 

80.79 
83.27 
75  70 

XII 

Sprayed  three  times  at  intervals  of  ten 
days  with  liquid  Bordeaux-Paris  green 

24.05 

48.80 

XIII 

Sprayed   six   times  at  intervals  of  ten 
days  with  dust  Bordeaux-Paris  green 

XV 

Sprayed   six  times   at   intervals  of  ten 
days  with  Bordeaux-Paris  green  mix- 
ture   

24.95 

77.10 

84.56 

XVIII 

Sprayed  only  once  during  entire  season 

37.71 

58.00 

III& 

VII 

Sprayed  three  times  early  in  season  for 
scab  and  codling'  moth      

69.49 

1907.  J     BITTER  ROT  OF  APPLES,  HORTICULTURAL,  INVESTIGATIONS.     533 

A  remarkable  feature  of  the  results  obtained  in  the  Blackledge 
orchard  is  the  demonstration  of  the  effect  of  the  three  early  spray- 
ings applied  for  apple  scab  and  codling  moth,  in  controlling  bitter 
rot.  In  every  instance,  as  will  be  seen  by  comparing  columns  one 
and  two  in  the  above  table,  the  percentage  gain  of  treated  plats  over 
absolutely  untreated  plats  was  from  23  percent  to  as  much  as  60 
percent  greater  than  the  gain  of  treated  plats  over  check  plats 
sprayed  three  times  for  apple  scab  and  codling  moth.  Comparing 
Plats  III  and  VII,  which  are  given  the  three  early  treatments  for 
apple  scab  and  codling  moth,  with  Plats  XI  and  XIV  which  were 
not  sprayed  during  the  entire  season,  the  two  early  treated  plats 
show  a  gain  over  the  two  untreated  plats  of  69.49  percent. 

CONCLUSIONS  FOR  1905 

Besides  confirming  various  conclusions  already  drawn  that  bitter 
rot  may  be  almost  completely  controlled  by  three  to  four  applica- 
tions of  Bordeaux  mixture  applied  at  intervals  of  ten  days  just 
previous  to  the  appearance  of  bitter  rot,  and  that  sprayings  after 
the  appearance  of  the  rot  are  of  some  benefit,  the  data  obtained  in 
1905  pointed  to  the  following  conclusions : 

1.  That  the  spring  sprayings  for  apple  scab  and  codling  moth 
are,  in  seasons  like  that  of  1905,  effective  in  controlling  a  very  con- 
siderable percentage  of  bitter  rot. 

2.  That  dust  spray  is  ineffective  in  combating  the  disease. 

3.  That  spraying  with  pure  copper  sulphate  solution  is  not  an 
effective  way  of  controlling  bitter  rot. 

IN  GENERAL 

WEATHKR  CONDITIONS  FAVORABLY  FOR  BITTER  ROT 

The  spasmodic  and  erratic  occurrence  of  the  disease  in  different 
seasons  has  long  been  noted  and  has  been  more  or  less  generally 
taken  as  indicating  a  relationship  between  the  weather  conditions 
and  the  development  of  the  fungus.  The  year  1900  proved  to  be  a 
year  of  exceptional  severity  in  the  attacks  of  the  disease  and  it  was, 
in  part,  the  uncommon  destructiveness  of  the  pest  during  that  year 
that  led  the  Horticultural  Department  of  the  University  of  Illinois 
to  inaugurate  this  line  of  work  looking  towards  the  discovery  of  a 
means  to  control  the  bitter  rot  fungus.  Yet  in  the  following  year, 
1901,  the  experimental  work. of  the  Department  was  rendered  null 
by  the  failure  of  bitter  rot  to  develop  in  orchards  where  the  disease 
had  been  prevalent  the  year  before.  In  reference  to  the  season  of 
1901,  Mr.  A.  V.  Stubenrauch,  who  had  charge  of  the  field  investi- 
gations that  year,  says :  "The  exceedingly  dry  hot  summer  seems 
to  have  been  very  unfavorable  for  the  development  and  spread  of 
bitter  rot.  Last  year,  1900,  the  disease  destroyed  practically  the 


534 


BULLETIN  No.  117. 


[August, 


entire  crop  wherever  it  made  its  appearance.  The  disease  has  not 
been  nearly  so  bad  this  year.  Many  orchards  badly  affected  last 
year  were  entirely  free  this  season;  many  were  only  slightly  af- 
fected and  no  case  of  a  total  failure  has  come  to  my  notice."*  The 
year  1902  proved  favorable  again  for  the  rot  and  in  all  the  orchards 
under  experimentation  check  plats  showed  an  infection  of  44  per- 
cent to  89  percent  of  the  total  crop.  In  1903  the  bitter  rot  was 
present  in  five  orchards  under  test  but  in  only  one  of  them  was  there 
an  infection  of  commercial  importance,  the  infection  in  the  excep- 
tional case  being,  however,  very  serious,  and  amounting  to  63  per- 
cent of  the  crop.  In  1904  the  disease  was  present  again  and  was 
apparently  more  general  in  its  spread.  It  was  more  destructive 
than  in  1903  but  less  so  than  in  1902,  in  the  orchards  which  were 
under  observation.  In  1905  only  two  orchards  were  under  experi- 
mentation, but  in  both  of  these  the  disease  was  sufficiently  serious 
to  destroy  from  14  to  35  percent  of  the  crop  in  the  untreated  plats. 
Comparing  different  seasons  in  the  same  orchard  it  will  be  seen  by 
reference  to  the  following  table  in  the  Tamaroa  orchard,  where 
three  seasons'  work  were  carried  on,  there  was  an  infection  of  68.54 
percent  in  1902,  1.27  percent  in  1903,  and  15.94  percent  in  1904. 
In  the  Flora  orchard  there  was  an  infection  in  1902  of  83.32  percent, 
in  1904  of  11.68  percent,  and  in  1905  of  14.63  percent.  A  glance  at 
the  table  of  infections  which  follows  will  serve  to  impress  still  fur- 
ther the  erratic  manner  in  which  the  disease  appears  from  season 
to  season : 


TABLE  26.- 


-PERCENTAGE  OP  BITTER  ROT  IN  UNTREATED  PLATS  DURING 
DIFFERENT  SEASONS  FROM  1902  to  1905 


Year 

Orchard. 

Per 

cent 
bitter 
rot. 

Year 

Orchard. 

Per 
cent 
bitter 
rot. 

1902 

Tonti  (Huntsman) 

89  27 

1904 

Flora    

11  68 

(Ben  Davis)  .  .    . 

44.95 

Olney  

1.18 

Tamaroa  

68  54 

Tainaroa  

15  94 

Flora  

83  32 

Kell      

21  50 

1903 

Olney  • 

.32 

1905 

Flora    

14.63 

Tatnaroa    

1  27 

Clav  Citv 

35.59 

New  Burnside  

3.51 

Carbondale  No   1  

7  05 

. 

Carbondale  No.  2  
(Jonathan  )  

62  97 

(  Winesap)  

23.69 

(Ben  Davis)   

63.09 

^Circular  No  43,  University  of  Illinois  Experiment  Station,  1902-p.  4. 


1907.]     BITTER  ROT  OF  APPLES,  HORTICULTURAL  INVESTIGATIONS.     535 


This  irregularity  in  the  behavior  of  bitter  rot  is  not  confined 
alone  to  different  seasons.  It  makes  its  appearance  in  different 
years  at  very  different  dates  and  in  different  orchards  it  may  occur 
at  more  or  less  widely  separated  intervals  in  the  same  season.  Bit- 
ter rot  is  a  disease  which  ordinarily  develops  comparatively  late  in 
the  season  causing  the  greatest  amount  of  damage  when  the  fruit 
is  fairly  well  matured  and  not  far  from  the  picking  stage  in  its  de- 
gree of  ripeness,  but  we  now  know  that  the  destruction  is  sometimes 
greatest  in  July  when  the  late  varieties  are  not  half  grown.  In- 
fected apples  in  orchards  subject  to  the  disease  are  found  at  various 
dates  during  the  months  of  June  and  July.  In  1902  the  first  record 
of  its  existence  on  young  apples  was  made  June  28th  but  the  speci- 
mens showed  that  the  infection  must  have  been  at  least  two  weeks 
earlier,  and  it  has  been  otherwise  sufficiently  proved  that  in  numer- 
ous instances  the  attack  occurs  as  soon  as  the  middle  of  June.  Some 
interesting  data  in  this  regard  appears  in  the  tabulation  following : 


TABLE  27.- 


-DATE  OF  FIRST  APPEARANCE  OF  BITTER  ROT  DURING  DIF- 
FERENT SEASONS 


Year. 

Owner  of  orchard. 

Location. 

County. 

Variety.    . 

Date  of  first 
appearance 
of  bitter  rot. 

1902 
1903 

1904 
1905 

J.  B.  Brokaw  
F.  L.  Williams  .. 
...       .  and  Son 

Tonti 

Tamaroa 
Flora 

Olney 

Tamaroa 
NewBurnside 

Carbondale 

Carbondale 

Flora 
Olney 

Tamaroa 
Kell 

Flora 
Clay  .City 

Marion 

Perry 
Clay 

Richland 

Perry 
Johnson 

Jackson 

Jackson 

Clay 
Richland 

Perry 
Marion 

Clay 
Clay 

Huntsman 

Ben  Davis 
WillowTwig 

Ben  Davis 

Ben  Davis 
Early  Harvest 
Ben  Davis 
Jonathan        ) 
Winesap 
Ben  Davis      ) 
Ben  Davis 

Willow  Twig 
Ben  Davis 

Ben  Davis 
Ben  Davis 

Willow  Twig 
Ben  Davis 

July  8th 

July  5th 
July  10th 

Aug.  7th 

July  6th 
June  25th 
Sept.  7th 

Aug.  5th 

Before 
Aug.  17th 
July  24th 
July  27th 

July  16th 
July  22d 

July  24th 
July  21st 

Dale  Mann  

J.  L.  Zook    

F.  L.  Williams  .  . 
and  Son 

J.  W.  Heaton  .... 
H   E.  Allen  

Charles  Allen  .  .  . 
Dale  Mann  

J    L    Zook     .... 

F.  L.  Williams  . 
and  Son  

W.  T.  Storment  . 
Dale  Mann  

John   Blackledge 

This  characteristic  irregularity  in  the  behavior  of  the  disease 
must  possess  some  significance  in  the  history  of  its  development,  and 
this  significance  must  be  concerned  either  with  the  conditions  con- 
trolling the  original  infection  or  the  conditions  controlling  the  viru- 
lence of  the  disease  after  infection  takes  place.  In  all  of  the  orchards 
under  experimentation  enough  bitter  rot  appeared  every  season  to 
infect  the  entire  crop,  under  conditions  favorable  to  the  growth  and 


536  BULLETIN  No.  117.  [August, 

spread  of  the  fungus,  Table  26.  The  characteristic  irregularity  of 
bitter  rot  must  therefore  be  due  to  the  presence  or  absence  of  those 
conditions  which  are  favorable  to  its  distribution  and  growth. 
What  then  are  the  circumstances  which  favor  the  development  of 
the  disease  ? 

In  Bulletin  No.  77  of  this  Station  it  was  stated  that  the  rapidity 
of  development  depends  upon  climatic  conditions.  It  is  essentially 
a  hot  weather  disease  and  moisture  is  necessary  for  the  distribution 
and  germination  of  the  spores.  It  is  true  that  the  infection  of  the 
fruit  sometimes  becomes  apparent  and  the  progress  of  the  disease 
is  abundantly  evident  when  the  atmosphere  is  very  dry;  but  this 
only  happens  after  the  fungus  has  gained  entrance  to  the  apples, 
which  must  have  occurred  during  a  previous  period  of  rainy  weather 
or  heavy  dews.  Moisture,  generally  in  the  form  of  rain,  and  high 
temperature  are  necessary  to  start  an  epidemic.  These  of  course  are 
only  favorable  conditions  for  the  development  of  the  fungus  which 
is,  itself,  the  direct  agent  of  destruction.  Fortunately  the  fungus  is 
not  very  resistant  to  unfavorable  conditions  and  may  sometimes  die 
out  entirely  during  one  year  where  it  has  been  previously  abundant. 
This,  with  its  power  of  enormous  multiplication  under  circumstances 
well  suited  to  its  growth,  sufficiently  accounts  for  the  marked  irregu- 
larity in  the  time  and  virulence  of  its  attack. 

Scott  says,  "The  predominating  conditions  that  influence  the 
development  of  bitter  rot  are  temperature  and  humidity.  A  few 
days  of  hot  showery  weather  may  start  an  epidemic  that  will  destroy 
the  entire  crop  of  certain  varieties,  provided  the  fungus  is  present. 

"Cold  is  decidedly  unfavorable  to  the  fungus  and  it  rarely  does 
any  damage  during  a  cool  season.  An  outbreak  may  be  almost 
completely  checked  by  a  few  days  of  cool  weather,  especially  when 
the  mean  temperature  remains  below  70  degrees  F."* 

Von  Schrenk  and  Spaulding  write  in  regard  to  this  point  that 
"The  factors  which  determine  the  time  of  the  appearance  of  the  dis- 
ease are  probably  (i)  the  age  of  the  fruits j  v  (2)  the  temperature 
and  humidity  of  the  air;  (3)  the  presence  of  spore  distributing 
centres. 

"Warm,  sultry  weather,  particularly  after  a  rain,  forms  the 
ideal  condition  for  the  development  of  bitter  rot.  In  cool  dry  sum- 
mers the  bitter  rot  is  usually  present  but  sparingly.  A  short  series 
of  hot,  wet  days  in  August  may  bring  about  a  sudden  and  very  de- 
structive attack.  Nights  with  a  heavy  fall  of  dew  alternating  with 
hot  days  are  usually  followed  by  an  extensive  development  of  the 
disease."** 

*The  control  of  Apple  Bitter  Rot,  \V.  M.  Scott.  U.  S.  Department  of 
Agriculture,  Bureau  of  Plant  Industry — Bulletin  No.  93.  pp.  12-14. 

**The  Bitter  Rot  of  Apples,  Von  Schrenk  and  Spaulding,  U.  S.  Depart- 
ment of  Agriculture,  Bureau  of  Plant  Industr3T — Bulletin  No.  44.  p.  15. 


1907.]     BITTER  ROT  OF  APPLES,  HORTICULTURAL  INVESTIGATIONS.      537 

If  the  prevalence  of  the  disease  in  different  seasons  be  referred 
to  the  weather  conditions  for  the  corresponding  seasons  there  should 
be  no  difficulty  in  settling  the  relation  between  the  virulence  of  the 
disease  and  the  climatic  conditions  obtaining  during  the  season.  The 
accompanying  tabulation  of  temperatures  and  rainfall  for  various 
points  in  southern  Illinois  is  compiled  from  records  in  the  Agron- 
omy Department  at  the  University  of  Illinois.  In  some  cases  the 
readings  appear  high  owing  to  the  class  of  thermometers  used  by 
some  observers,  but  as  the  readings  are  merely  for  relative  references 
in  this  connection,  they  are  sufficiently  accurate  to  serve  the  purpose 
of  comparisons,  pp.  538-540. 

It  will  be  noted  that  in  the  year  1900  when  the  bitter  rot  was 
so  enormously  destructive  in  the  southern  part  of  the  state  the  month 
of  June  was  exceptionally  wet,  nearly  twice  the  average  rainfall  for 
that  month  being  noted  at  Flora,  Mount  Vernon,  and  Centralia,  and 
two  inches  more  than  the  average  at  Olney.  The  mean  temperature 
for  the  year  proved  to  be  one  to  three  degrees  lower  than  the  aver- 
age but  still  from  2.4  to  4.2  degrees  warmer  than  that  mentioned 
by  Scott  as  being  favorable  to  the  growth  of  the  fungus,  i.  e-  70 
degrees  F.  July  also  proved  unusually  wet,  considerably  more  than 
the  average  amount  of  rain  falling  at  all  points  except  Centralia, 
and  the  weather,  while  not  exceptionally  warm  for  the  district, 
ranged  from  5.5  to  8.2  degrees  above  70  degrees  F.  August  proved 
to  be  dry,  the  precipitation  falling  considerably  below  the  average, 
but  the  damage  had  already  been  done  and  the  infection  was  com- 
plete during  the  preceding  months.  The  year  1901,  which  has  al- 
ready been  referred  to  as  a  season  in  which  little  bitter  rot  occurred, 
offers  an  interesting  contrast  in  respect  to  moisture  conditions  to  the 
preceding  year.  In  every  instance  during  the  months  of  June  and 
July  the  rainfall  is  markedly  below  the  yearly  average,  and  even  the 
precipitation  during  the  month  of  August,  which  proved  to  be  a 
little  more  than  the  average  for  that  month,  is  not  excessive,  the 
largest  fall  recorded  being  3.52  inches  for  the  month.  The  prevail- 
ing temperatures  throughout  were  higher  than  their  respective  aver- 
ages. The  conditions  and  results  of  these  two  seasons  bear  out  very 
clearly  the  contention  that  warm  moist  conditions  are  favorable  to 
the  spread  of  the  disease  and  tend  to  discredit  the  theory  advanced 
some  years  ago  in  certain  quarters  that  it  is  a  hot  dry-weather 
fungus.* 

The  season  of  1902  as  shown  by  the  results  of  the  work  in  .the 
experimental  plats,  Table  26,  proved  favorable  again  to  the  dis- 
ease, though  reports  from  commercial  quarters  did  not  indicate  so 


*Note  reference  to  this  theory  by  Burrill,  Transactions  Illinois  Horticul- 
tural Society,  1901,  p.  186. 


538 


BULLETIN  No.  117. 


[August, 


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1907.]     BITTER  ROT  OF  APPLES,  HORTICULTURAL  INVESTIGATIONS.     541 

severe  an  attack  as  in  1900.  Glancing  at  the  weather  conditions  for 
1902  we  find  a  period  of  high  temperatures  and  more  than  the  aver- 
age amount  of  rainfall  for  the  month  of  June,  average  temperatures 
and  a  moderate  rainfall  for  July,  and  moderate  temperatures  and 
more  than  an  average  rainfall  during  August.  The  extremes  of  the 
two  preceding  seasons  were  absent  and  the  bitter  rot  showed  itself 
with  less  destructiveness  than  in  1900  but  with  more  than  in  1901. 
The  succeeding  seasons  afford  data  very  similar  to  those  already 
noted,  but  some  further  facts  of  interest  in  this  regard  are  furnished 
by  the  data  for  1903,  1904,  and  1905.  In  1903  the  precipitation 
proved  about  normal  for  June  and  July  but  above  the  average  in 
most  cases  for  August,  with  the  result  that  the  bitter  rot  appeared 
late  in  the  season,  the  first  infection  occurring,  with  one  or  two  ex- 
ceptions in  August,  Table  27.  During  the  following  two  years 
the  heavy  rainfall  occurred  during  July,  and  without  exception  the 
infection  of  bitter  rot  occurred  during  that  month. 

It  may  be  safely  concluded  that  moist  weather  with  a  consider- 
able precipitation  and  a  high  temperature  are  favorable  to  the  spread 
and  growth  of  bitter  rot.  There  was  no  opportunity  to  note  the 
effect  of  moist  cold  weather  though  it  might  be  argued  from  analogy, 
there  being  no"  evidence  of  the  disease  in  Northern  and  very  little  in 
Central  Illinois,  where  the  rainfall  is  abundant  and  the  mean  tem- 
perature lower,  that  moisture  without  high  temperature  is  not  favor- 
able to  the  development  of  the  disease.  Hot  weather  alone  unac- 
companied by  moisture  proved  unfavorable  to  the  spread  of  the  dis- 
ease, as  seen  in  the  season  of  1901,  but  hot  weather  alone  did  not 
prevent  the  disease  from  accomplishing  its  work  of  destruction  after 
infection  had  once  occurred,  as  was  observed  in  1900  when  the  dry 
month  of  August  followed  the  abnormally  wet  months  of  June 
and  July. 

EFFECT  OF  SPRAYING  ON  BITTER  ROT 

That  spraying  will  control  ninety  percent  or  more  of  the  damage 
liable  to  occur  from  bitter  rot  when  the  proper  materials  are  applied 
at  the  proper  tin^e  and  in  the  proper  way  has  been  conclusively  dem- 
onstrated in  a  considerable  number  of  instances.  In  1902  as  much 
as  91.26  percent  of  the  fruit  liable  to  attack  by  bitter  rot  was  saved 
in  an  orchard  at  Tonti,  where  there  was  an  infection  of  the  disease 
in  the  check  plat  amounting  to  44.95  percent,  Table  2.  In  1903 
trees  sprayed  only  twice  for  the  disease  showed  an  average  saving 
of  59.85  percent,  where  62.97  percent  of  the  entire  crop  was  in- 
fected, Tables  13  and  14.  In  1904  as  much  as  98.20  percent 
was  saved  in  an  orchard  at  Kell,  where  20  to  23  percent  of  the  fruit 
on  the  check  plats  showed  infection,  Tables  18  and  19.  In 
1905,  92.14  percent  of  the  fruit  liable  to  the  disease  was  saved  in  an 


542  BULLETIN  No.  117.  [August, 

orchard  at  Flora,  where  one  check  plat  showed  10.49  percent  of 
infected  fruit  and  a  second,  27.78  percent,  and  three  check  plats 
showed  an  average  of  14.63  percent,  Tables  24  and  25. 

While  the  remarkably  favorable  results  above  mentioned  were 
obtained  only  under  certain  specific  treatments  and  not  in  every 
experiment,  they  were  obtained  in  nearly  every  orchard  which 
showed  a  uniform  and  considerable  infection  of  the  disease,  and  in 
every  year  of  the  series  except  1901  when  the  rot  failed  to  appear  in 
the  plats  selected  for  experimentation.  Moreover,  leaving  out  of 
consideration  these  more  successful  treatments,  it  appeared  that 
spraying,  in  almost  every  instance,  whether  applied  late  or  early, 
seldom  or  frequently,  showed  some  degree  of  effectiveness  in  con- 
trolling the  disease,  its  effectiveness  ranging  from  ten  to  ninety 
percent  according  to  circumstances. 

TIME;  OF  SPRAYING  FOR  BITTER  ROT 

1.  Early  or  spring  sprayings  for  apple  scab  and  codling  moth: 
The  experiments  performed  in  the  John  Blackledge  orchard  at  Clay 
City,  in  1905,  indicated  a  possible  saving  in  plats  sprayed  three  times 
early  in  the  season  for  apple  scab  and  codling  moth,  of  69.49  percent, 
over  plats  which  received  no  early  treatment.     In  many  instances, 
however,  in  other  orchards,  the  total  saving  effected  by  the  three  . 
early  sprayings,  together  with  various  subsequent  ones,  amounts  to 
less  than  a  total  of  69.49  percent.     Therefore,  we  must  conclude 
that  the  circumstances  in  the  orchard  at  Flora,  in  1905,  were  some- 
what exceptional,  and  that  so  complete  a  saving  is  not  to  be  de- 
pended upon  by  the  orchardist.    There  is  no  doubt,  however,  that, 
in  seasons  like  that  of  1905,  some  degree  of  protection  is  afforded 
by  these  early  sprayings. 

2.  Spraying  after  the  early  treatments  for  apple  scab  and  codling 
moth  and  before  the  appearance  of  the  disease:    In  every  instance 
where  this  treatment  was  given  the  amount  of  bitter  rot  was  either 
comparatively  or  actually  small.     The  more  complete  the  general 
infection,  the  more  clearly  defined  was  the  effect  of  spraying  at  this 
time  in  reducing  the  amount  of  bitter  rot.    There  were,  of  course,  a 
number  of  variations  of  this  treatment,  due  to  the  very  considerable 
period  of  time  which  usually  elapsed  between  the  date  of  the  last 
spraying  for  apple  scab  and  codling  moth  and  the  date  of  the  first 
infection  of  bitter  rot ;  as,  for  example,  three  sprayings  at  intervals 
of  ten  days  after  the  third  early  treatment  for  apple  scab  and  codling 
moth ;    four  sprayings  at  intervals  of  one  week  during  June ;   three 
sprayings  at  intervals  of  ten  days  commencing  about  July  1st,  and 
others.     Of  these  treatments  the  most  effective  were  those  which 
were  applied  most  shortly  before  the  appearance  of  the  rot.    In  1902 


\ 

1907.]     BITTER  ROT  OP  APPLES,  HORTICULTURAL  INVESTIGATIONS.     543 

the  most  successful  treatment  was  one  in  which  a  plat  was  treated 
five  times  before  the  appearance  of  bitter  rot,  the  last  spraying  being 
made  July  2d,  six  days  before  bitter  rot  appeared.  This  plat  was 
also  sprayed  once  after  the  discovery  of  the  disease,  but,  as  other 
plats  sprayed  after  the  appearance  of  the  fungus  showed  compara- 
tively little  benefit  from  the  treatment,  it  may  be  concluded  that  the 
high  degree  of  protection  evidenced  by  this  plat  is  not  to  be  attrib- 
uted to  the  last  spraying,  Table  2.  In  the  orchard  of  H.  E.  Al- 
len at  Carbondale,  where  the  best  results  were  obtained  in  1903, 
the  highest  degree  of  protection -was  afforded  by  plats  sprayed  twice 
before  the  appearance  of  the  disease.  The  treatments,  which  were 
given  June  26th  and  July  ist,  were  apparently  too  early  to  give  the 
best  results,  for  bitter  rot  did  not  appear  until  August  5th,  and  in- 
stead of  saving  over  90  percent  of  the  fruit  liable  to  infection,  there 
was  a  saving  of  only  49.39  percent  in  the  case  of  Ben  Davis,  69.44 
percent  in  the  Winesap,  and  60.71  percent  in  the  case  of  Jonathan, 
Table  14.  In  1904  the  most  conclusive  results  were  obtained 
in  the  orchard  at  Kell.  Here  three  different  treatments  were  given 
during  the  two  months  preceding  the  first  appearance  of  bitter  rot 
and  all  were  remarkably  successful  in  controlling  the  disease.  The 
last  spraying  in  each,  however,  was  given  but  a  short  time  before 
the  'date  when  the  first  infection  was  discovered,  July  22d.  Plat 
IV  was  sprayed  twice  before  the  appearance  of  the  disease  and  once 
after,  July  9th,  i9th  and  29th  and  it  afforded  a  slightly  less  perfect 
protection  than  the  treatments  given  Plats  V  and  VI,  in  which  all 
the  sprayings  were  given  previous  to  the  first  discovery  of  the  fun- 
gus. Plat  V,  which  was  sprayed  May  3Oth,  June  8th,  2Oth,  29th, 
and  July  9th,  evidenced  the  most  complete  control  of  the  three,  pro- 
tecting 98.20  percent  of  the  fruit  liable  to  attack  by  the  disease. 
Plat  VI,  sprayed  at  weekly  intervals  throughout  June,  protected 
95.42  percent  of  the  fruit  liable  to  infection  and  stood  second  in  ef- 
fectiveness. It  must  be  noted,  however,  that  this  plat  received  four 
sprayings  and  Plat  V,  five  sprayings,  as  compared  with  only  three 
sprayings  for  Plat  IV,  one  of  which  was  after  the  appearance  of  the 
rot;  and  yet  the  control  in  Plat  IV  amounted  to  94.59  percent, 
showing  an  efficiency  almost  equal  to  that  of  the  more  elaborately, 
but  earlier  treated  plats.  It  seems  very  likely  indeed  that,  had  the 
third  treatment  been  given  just  before  the  infection  occurred,  the 
protection  would  have  been  as  great  in  this  plat  as  in  the  others. 
At  any  rate  it  indicates  that  the  most  effective  sprayings  are  those 
which  are  applied  most  shortly  before  the  first  bitter  rot  infection 
occurs,  Tables  18  and  19.  In  1905  in  both  the  Flora  and  the 
Clay  City  orchards  the  greatest  protection  was  afforded  by  three 
applications  of  Bordeaux  at  intervals  of  ten  days  during  July.  Bit- 
ter rot  appeared  in  the  former  orchard  on  July  25th  and  the  third 


544  BULLETIN  No.  117.  [August, 

spraying  occurred  on  that  date,  thus  bringing  these  sprayings  im- 
mediately up  to  the  time  of  the  first  infection.  The  disease  appeared 
in  the  orchard  at  Clay  City  on  July  2ist,  so  that  the  third  spraying 
was  given  shortly  after  the  first  infection,  Tables  22  to  25. 

3.  Spraying  so  as  to  coat  the  fruit  thoroughly  as  soon  as  bitter 
rot  appears:    Although  not  so  successful  a  treatment  as  spraying 
at  intervals  of  a  week  to  ten  days  just  previous  to  the  first  infection, 
spraying  so  as  to  coat  the  apples  thoroughly  as  soon  as  the  disease 
appeared   had  a  marked  effect  in  reducing  the  loss  from  bitter  rot. 
This  treatment  was  first  given  in  1904,  and  in  the  Kell  orchard, 
where  it  proved  most  successful  that  year,  it  effected  a  saving  of 
72.02  percent  over  the  check  plats  as  compared  with  a  saving  of 
94.59  percent  effected  in  a  plat  sprayed  twice  previous  to  the  first 
infection     and  once    immediately    after   the   infection,   Table    19. 
In  the  Flora  orchard  in  1905  this  treatment  resulted  in  a  saving  of 
71.63  percent  as  compared  with  a  saving  of  92.14  percent  in  the 
most   successful   plat,    Table   23.      During   the   same   season    an- 
other plat  similarly  treated  in  the  orchard  at  Clay  City  showed  a 
saving  of  75.19  percent  compared  with  a  saving  of  90.05  percent  in 
the  most  successful  plat,    Table  25.    It  would    appear,    therefore, 
that  this  treatment  is  to  be  strongly  recommended  to  those  fruit, 
growers  who  find  their  orchards  unexpectedly  attacked  by  the  dis- 
ease and  who  have  neglected  to  give  the  earlier  sprayings  as  a  mat- 
ter of  precaution.    In  this  connection  special  attention  must  be  called 
to  the  fact  that  this  treatment  was  always  given  as  soon  as  the  first 
infected  apple  was  found  and  not  when  the  diseased  apples  had  be- 
come numerous  and  rot  thoroughly  established.     Moreover  to  coat 
the  fruit  thoroughly  with  spray  it  is  necessary  to  make  three  appli- 
cations, the  second  application  being  made  after  the  first  has  dried 
and  the  third  after  the  second  has  dried. 

4.  Spraying  after  bitter  rot  has  become  thoroughly  established : 
Tests  of  this  treatment  proved  uncertain  and  gave  varying  results. 
In  some  instances  a  considerable  degree  of  protection  was  afforded 
and  in  others  very  little  or  no  benefit  resulted.     This  fact  taken  in 
connection  with  the  habit  of  the  fungus  itself  of  growing  among  the 
tissues  of  the  fruit  beneath  the  skin  would  appear  to  indicate  that 
spraying  after  the  fungus  has  gained  an  entrance  into  the  fruit  is 
useless  as  a  means  of  controlling  the  disease,  but  that  this  late  spray- 
ing may  in  some  cases  be  the  means  of  preventing  the  spread  of  the 
disease  from  affected  to  unaffected  apples.     In  1902  a  number  of 
plats  were  treated  after  the  disease  was  fully  established.    A  plat  in 
the  Tamaroa  orchard  sprayed  five  times  after  the  disease  was  fully 
established  gave  a  saving  of  29.59  percent  over  a  check  plat;   a  plat 
sprayed     three     times     showed     a  saving  of  12.52  percent,  Table 
5 ;  two  plats  in  the  Flora  orchard  sprayed  five  times  after  th'e  ap- 


1907.]      BITTER  ROT  OF  APPLES,  HORTICULTURAL  INVESTIGATIONS.      545 

pearance  of  the  disease  showed  a  saving  of  28.12  percent  as  a  result 
of  this  treatment,  Table  7.  In  1903,  in  the  only  orchard  which 
afforded  definite  data,  that  of  Mr.  H.  E.  Allen  at  Carbondale,  the 
plats  sprayed  after  the  appearance  of  the  disease  gave,  with  the  ex- 
ception of  the  Winesap  plat,  a  higher  percentage  of  bitter  rot  than 
the  check  plats.  The  Winesap  plat  showed  some  gain  over  the  check 
plat  but  the  entire  infection  was  less  among  the  fruits  of  that  variety 
than  among  the  fruits  of  the  other  two  varieties,  Jonathan  and  Ben 
Davis,  Table  13.  In  1904  in  the  Kell  orchard  the  late  treat- 
ment proved  quite  successful,  resulting  in  a  gain  over  the  check 
plats  of  81.91  percent.  The  best  plat  of  the  series,  however,  gave  a 
saving  of  98.20  percent  of  all  the  fruit  liable  to  infection,  or  16.29 
percent  more  than  the  late  sprayed  plat,  Table  19.  These  results 
indicate,  therefore,  the  unreliability  of  this  treatment  and  suggest 
that  it  should  be  applied  only  as  a  desperate  expedient  in  cases  where 
carelessness  or  force  of  circumstances  have  prevented  earlier  treat- 
ments and  not  as  a  certain  or  infallible  remedy. 

5.  Spraying  dormant  wood :  Since  the  bitter  rot  fungus  passes 
the  winter  in  cankers  on  the  branches  of  the  trees  and  also 
in  the  mummies  which  sometimes  remain  on  the  trees,  it  was 
thought  that  treatment  of  the  dormant  wood  might  destroy  the  fun- 
gus in  this  stage  and  prevent  fresh  infection  the  next  year.  In  1903 
plats  were  sprayed  in  the  orchards  at  Olney  and  at  Tamaroa  with  a 
copper  sulphate  solution,  one  in  each  orchard  in  the  fall  and  one  in 
the  spring,  while  the  trees  were  dormant.  There  was  as  much  rot 
in  these  plats  as  in  the  check  plats,  but  as  very  little  rot  developed  in 
any  of  the  plats  the  results  were  inconclusive,  Tables  9  and 
10.  In  1904  two  plats  in  the  Kell  orchard,  one  treated  with 
Oregon  Wash,  and  one  treated  with  copper  sulphate  solution, 
showed  even  more  rot  than  the  check  plats,  25.17  percent  and  28.81 
percent,  respectively,  of  the  entire^  crop,  being  affected  Table 
1 8.  The  average  results  for  all  the  orchards  treated  in  1904  show 
that  there  was  a  slightly  greater  loss  of  fruif  from  bitter  rot  in  the 
plats  which  were  treated  on  the  dormant  wood  than  in  the  check 
plats,  amounting  in  case  of  Oregon  Wash  to  10.93  percent  of  the 
entire  crop,  and  in  case  of  copper  sulphate  solution  to  12.44  percent, 
as  compared  with  10.52  percent  for  the  check  plats,  Table  20. 
These  results  are  considered  sufficiently  decisive  to  warrant  the  con- 
clusion that  spraying  the  dormant  wood  is  entirely  ineffective  in 
controlling  bitter  rot. 

MATERIALS  FOR  SPRAYING 

i.  Liquid  Bordeaux  mixture:  Liquid  Bordeaux  mixture  made 
up  in  the  proportions  of  four  pounds  of  copper  sulphate,  four  pounds 
of  lime,  and  fifty  gallons  of  water  was  the  fungicide  used  in  the 


546  BULLETIN  No.  117.  [August, 

great  majority  of  the  tests.  To  this  mixture  were  commonly  added 
four  ounces  of  Paris  green  as  an  insecticide,  but  this  material  was 
not  expected  to  act  in  connection  with  the  copper  sulphate  as  a  pre- 
ventive of  bitter  rot.  It  is  sufficient  to  say  that  all  the  most  suc- 
cessful treatments  were  obtained  by  the  use  of  this  fungicide. 

2.  Soluble  Bordeaux  mixture :    Soluble  Bordeaux  mixture  was 
used  in  but  one  instance,  being  applied  to  Plat  II  in  the  Mann  or- 
chard at  Flora  in  1905.    It  resulted  in  a  saving  of  78.06  percent  as 
compared  with  a  saving  of  68.42  percent  in  one  plat  similarly  treated 
with  regular  Bordeaux  and  of  81.00  percent  in  a  second  plat  treated 
with  the  regular  Bordeaux  mixture.     Its  efficiency  in  this  test  ap- 
peared to  be  equal  to  Bordeaux  mixture  prepared  in  the  usual  man- 
ner, Table  23. 

3.  Dust  Bordeaux  mixture :    Dust  Bordeaux  mixture  proved  a 
failure  as  a  means  of  controlling  bitter  rot.    It  was  tried  in  the  or- 
chard at  Clay  City  in  1905.    Plat  XIII  in  that  orchard  was  sprayed 
three  times  at  intervals  of  ten  days  beginning  ten- days  after  the  third 
treatment  for  apple  scab  and  codling  moth,  and  compared  with  an 
adjoining  plat  similarly  treated  with  liquid  Bordeaux  mixture.   The 
dust  sprayed  plat  showed  an  infection  of  52.79  percent  of  the  entire 
crop  as  compared  with  27.03  percent  for  the  liquid  sprayed  plat 
beside  -it.     In  fact  the  dust  sprayed  plat  which  received  with  the 
three  early  sprayings  for  'apple  scab  and  codling  moth,  a  total  of  six 
applications  during  the,  season,  showed  a  higher  infection  of  bitter 
rot  than  any  other  plat  in  the  orchard  including  the  untreated  plats 
which  had  been  left  as  checks,  Table  24. 

4.  Pure  Copper  Sulphate  Solution :    Pure  copper  sulphate  solu- 
tion was  tried  in  varying  strengths  during  two  seasons.     In  1904 
two  plats  in  the  Kell  orchard  were  sprayed  with  copper  sulphate 
solution.     In  the  first,  where  eight  ounces  of  copper  sulphate  were 
used  to  fifty  gallons  of  water,  ^there  was  an  infection  amounting  to 
26.95  percent  of  the  entire  crop,  or  about  5  percent  more  than  ap- 
peared in  the  untreate'd  or  check  plats.     In  the  second  plat,  where 
ten  ounces  of  copper  sulphate  were  used  to  fifty  gallons  of  water, 
there  was  an  infection  of  18.48  percent  of  the  crop,  or  a  gain  over 
the  check  plats  of  about  3  percent.     It  will  be  remembered,  in  com- 
parison with  these  results,  that  in  this  orchard  three  different  treat- 
ments with  Bordeaux  mixture  gave  almost  perfect  control  over  the 
rot,  Table  18.     In  the  following  year,  1905,  Plat  IX  in  the  orch- 
ard at  Clay  City  was  sprayed  with  a  solution  of  copper  sulphate 
consisting  of  three  pounds  of  the  salt  to  fifty  gallons  of  water.   12.83 
percent  of  the  fruit  in  the  plat  was  lost  by  bitter  rot  as  compared 
with   about    10.00   percent    in   the      two  check     plats,     Table  24. 
The  evidence  is  then  overwhelmingly  against  the  use  of  pure  copper 
sulphate  solution  as  a  fungicide,  and  when  to  its  ineffectiveness  in 
controlling  the  bitter  rot  is  added  the  fact  that  it  caused  great  dam- 


1907.}     BITTER  ROT  OF  APPLES,  HORTICULTURAL  INVESTIGATIONS.      547 

age  to  the  foliage  of  a  number  of  the  trees  treated,  it.  is  apparent 
that  this  treatment  is  not  only  useless  as  a  remedy  for  bitter  rot  but 
is  also  a  menace  to  the  trees.  Its  ineffectivenss  when  applied  to  the 
dormant  wood  has  already  been  referred  to  under  another  heading. 
5.  Oregon  Wash :  Oregon  Wash  was  applied  only  to  the  dor- 
mant wood.  The  percentage  of  bitter  rot  was  a  trifle  less  in  plats 
sprayed  with  this  preparation  than  in  plats  sprayed  with  the  copper 
sulphate  solution  but  the  difference  was  insignificant,  not  being 
greater  than  might  be  accounted  for  by  differences  in  the  original 
amounts  of  infection  in  the  plats  themselves,  and  both  proved  about 
equally  ineffective  in  controlling  the  disease,  Table  20. 

APPLICATIONS  OF  SALT  TO  THE  GROUND 

The  statement  having  appeared  in  some  quarters  that  applica- 
tions of  salt  to  the  soil  under  the  trees  had  helped  to  control  bitter 
rot,  the  treatment  was  given  in  comparison  with  other  treatments  in 
the  season  of  1905.  One  plat  in  the  Flora  orchard  and  one  plat  in 
the  Clay  City  orchard  were  treated  with  twenty-five  pounds  of  salt 
per  tree.  In  the  Flora  orchard  the  plat  thus  treated  showed  an 
infection  amounting  to  18.17  percent  of  the  crop,  or  somewhat 
higher  than  the  average  of  the  check  plats,  Table  22.  In  the 
Clay  City  orchard  the  plat  treated  with  salt  was  infected  to  the  ex- 
tent of  6.07  percent  of  the  entire  crop,  or  about  4  percent  less  than 
the  average  of  the  check  plats,  Table  24.  Since  the  results  vary 
somewhat  from  each  other  but  do  not  in  either  case  deviate  very 
widely  from  the  check  plats,  it  would  appear  that  the  difference  is 
due  rather  to  fluctuations  in  the  amount  of  the  infection  of  these 
particular  plats  than  to  differences  in  the  action  of  the  salt  in  con- 
trolling the  disease  on  the  two  plats.  Considering,  therefore,  that 
the  treatment  very  evidently  failed  in  the  Flora  orchard  and  showed 
so  small  a  difference  in  the  Clay  City  orchard  as  to  be  accounted  for 
by  the  factor  of  variation  in  infection,  it  is  concluded  that  applica- 
tions of  salt  to  the  ground  under  the  trees  are  useless  as  preventives 
of  bitter  rot. 

CONCLUSIONS 

1.  Bordeaux  mixture  properly  made  and  applied  will  save  over 
90  percent  of  the  fruit  liable  to  attack  by  bitter  rot. 

2.  Fruit  sprayed  in  such  a  manner  as  to  be  thoroughly  coated 
with  the  spray  mixture  when  the  first  infection  of  the  disease  appears 
will  be  injured  least  by  bitter  rot. 

3.  Spraying  until  the  fruit  is  completely  coated  with  the  mixture 
as  soon  as  the  first  infection  of  bitter  rot  is  discovered  is  of  consid- 
erable value  but  is  much  less  effective  than  the  treatment  mentioned 
above. 


548  BULLETIN  No.  117.  [Auyu&t, 

4.  Spraying  until  the  fruit  is  completely  coated  with  the  mixture 
after  bitter  rot  has  become  thoroughly  established  is  effective  in 
controlling  as  much  as  50  percent  of  the  disease  during  some  sea- 
sons.   In  other  seasons  its  effect  as  a  remedy  is  very  slight. 

5.  Bordeaux  mixture  applied  in  the  liquid  form  is  the  most  ef- 
fective spraying  material  for  the  control  of  apple  bitter  rot. 

6.  Dust  spray  is  ineffective  in  preventing  bitter  rot. 

7.  Pure  copper  sulphate  solution  failed  to  check  the  disease  and 
caused  injury  to  the  foliage. 

8.  To  coat  fruit  thoroughly  with  the  mixture  it  is  necessary  to 
make  at  least  three  applications  of  the  spray  material. 

9.  Applications  of  twenty-five  pounds   of  salt  to  the  ground 
about  a  tree  have  no  value  in  checking  the  disease. 

10.  The  conditions  most  favorable  for  the  development  of  bitter 
rot  are  ( i )  a  period  of  hot  weather  accompanied  by  frequent  rains 
and  heavy  dews  at  a  period  when  the  apple  crop  is  approaching  ma- 
turity, i.  e.,  from  the  middle  of  July  to  the  end  of  August.     (2) 
Numerous  sources  of  infection,  i.  e.,  cankers  on  the  limbs  and  mum- 
mied fruits  left  hanging  upon  the  trees. 

RECOMMENDATIONS  FOR  THE  TREATMENT  OF  BITTER  ROT 

1.  In  addition  to  the  three  early  sprayings  for  apple  scab  and 
codling  moth  make  applications  of  Bordeaux  mixture  at  intervals 
of  ten  days  commencing  the  third  week  in  June  and  continuing  the 
operation  until  the  appearance  of  bitter  rot,  or,  in  case  bitter  rot 
fails  to  appear,  until  the  end  of  July ;   in  all,  four  applications  if  the 
rot  appears  before  the  end  of  July,  or  five  applications  if  it  does  not. 

NOTE — In  most  seasons  three  applications  of  standard  Bordeaux  mixture, 
one  applied  the  last  week  in  June  arid  the  two  following-  at  intervals  of  ten 
days,  are  sufficient  to  prevent  the  disease.  Owing-,  however,  to  the  irregular- 
ity of  the  time  of  infection  in  different  seasons  this  practice  is  not  wholly 
safe,  and  the  extra  treatments  are  recommended  as  a  wise  precaution. 

2.  In  case  the  precautionary  sprayings  above  recommended  are 
not  given,  the  most  thorough  sprayings  to  coat  the  fruit  completely 
with  Bordeaux  mixture  should  be  given  on  the  first  discovery  of  bit- 
ter rot  in  the  orchard.     Failure  to  spray  promptly  at  this  time  will 
result,  in  a  season  favorable  for  the  development  of  the  disease,  in 
almost  complete  destruction  of  the  crop. 

3.  Mummies  of  apples  which  remain  upon  the  tree  during  the 
winter  should  be  picked  off  and  destroyed  in  order  to  eliminate  this 
source  of  infection  the  following  summer. 

4.  In  the  accompanying  bulletin  on  the  botany   of  bitter  rot 
(No.  118)  by  Dr.  T.  J.  Burrill   will  be  found  a  full  account  of  the 
bitter  rot  canker,  one  of  the  form's  in  which  the  fungus  is  carried 
over  winter.     The  cankers  should  be  cut  off  and  burned,  the  limb 


1907.]     BITTER  ROT  OF  APPLES,  HORTICULTURAL  INVESTIGATIONS.     549 

being  cut  a  few  inches  below  the  cankered  spot.  Care  should  be 
taken  not  to  cause  fresh  bruises  in  the  bark  of  other  branches  while 
this  operation  is  being  performed,  and  the  pruning  tools  should  not 
be  allowed  to  touch  the  canker  for  fear  of  carrying  the  infection  to 
the  freshly  cut  surfaces  below  the  diseased  bark. 

ACKNOWLEDGMENTS 

I  wish  at  this  time  to  convey  my  grateful  acknowledgments  to 
the  many  persons  who  have  assisted  in  carrying  out  the  experiments 
outlined  in  this  bulletin,  particularly  to  the  owners  of  the  various 
orchards  who  so  kindly  placed  their  trees  at  the  disposal  of  the 
Department  of  Horticulture,  and  to  the  Department  Assistants  on 
whose  faithful  attention  to  the  details  of  the  various  experiments 
the  success* of  the  work  largely  depended.  At  various  times  the 
following  Department  men  have  been  connected  with  this  work : 

Mr.  A.  V.  Stubenrauch,  who  had  charge  of  field  work  dur- 
ing 1901  and  a  part  of  1902. 

Mr.  R.  A.  Simpson,  who  conducted  the  experiments  in  the  Simp- 
son orchard  at  Parkersburg  in  1901. 

Mr.  W.  S.  Hotchkiss,  who  was  in  charge  of  field  investigations 
in  1902. 

Mr.  H.  Hasselbring,  who  was  in  charge  of  botanical  inves- 
tigations in  1902. 

Mr.  A.  W.  Bryant,  who  had  charge  of  field  work  in  the  Tama- 
roa,  Flora,  and  Tonti  orchards  .in  1902. 

Mr.  G.  M.  Bradford,  for  a  part  of  the  season  of  1903  in  charge 
of  the  New  Burnside  and  Carbondale  orchards- 

Professor  Charles  S.  Crandall,  who  was  responsible  for  the  ex- 
periments in  the  Flora,  Tamaroa,  and  Olney  orchards  in  1903  and 
for  a  large  amount  of  the  record  work  in  1904  and  1905. 

Mr.  C.  B.  Dull,  who  was  in  charge  of  the  field  work  at  Flora, 
Tamaroa,  and  Olney  in  1903,  and  at  Flora  and  Olney  in  1904. 

Mr.  R.  B.  Howe,  who  conducted  the  field  work  at  Tamaroa  and 
Kell  in  1904,  and  at  Flora  in  1905. 

Mr.  J.  R.  Shinn,  who  was  in  charge  of  the  field  work  at  Clay 
City  in  1905. 

Mr.  B.  S.  Pickett,  who  has  collected  and  arranged  the  data 
gathered  during  the  progress  of  the  experiments  and  has  prepared 
the  various  tables  presented  in  this  bulletin. 


550 


BULLETIN  No.  117. 


[August, 


TREE  No.  8  OF  PLAT  No.  12.  CLAY  CITY  ORCHARD.  SPRAYED  WITH  STAND- 
ARD BORDEAUX  MIXTURE.  TOTAL  APPLES,  2257;  APPLES  AFFECTED  BY  BITTER 
ROT,  443;  PERCENTAGE  AFFECTED  BY  BITTER  ROT,  19.63.  PHOTOGRAPH  SEPTEM- 
BER 26,  1905. 


1907.]      BITTER  ROT  OF  APPLES,  HORTICULTURAL  INVESTIGATIONS.      551 


TREE  No.  10  OF  PLAT  No.  11.    CLAY  CITY  ORCHARD.  CHECK,  NOT  SPRAYED. 

TOTAL  NUMBER  OF  APPLES,  2110:  NUMBER  OF  APPLES  AFFECTED  BY  BITTER 

ROT,  933;  PERCENTAGE  AFFECTED  BY  BITTER  ROT,  44.22.  PHOTOGRAPH  SEPTEM- 
BER 26,  1905. 


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